How many rounds does a data engineer interview loop have?

5 typical rounds: SQL (95 percent of loops), Python (70 percent), data modeling (55 percent), pipeline architecture or system design (52 percent of senior-and-above loops), and PySpark (30 percent at Spark-first companies). Phone screens are usually SQL plus a take-home or a 60-minute design walkthrough. Onsites add the remaining rounds plus a behavioral round.

What is the difference between a mid-level and senior data engineer loop?

Mid-level (L4) loops weight correctness and clean code: did you produce a working solution that handles the obvious edge cases. Senior (L5) loops weight trade-off articulation and failure-mode naming: did you name 2 alternatives, defend the choice, and call out what happens when the upstream dies on a holiday. Staff (L6) loops weight adapt-on-the-fly behavior: when the interviewer changes the SLA from 15-minute freshness to 1-minute mid-round, did you pivot cleanly.

Do all data engineer interviews include a Spark round?

No. Spark-first companies (Databricks, Netflix, Uber, Airbnb, DoorDash, Spotify) test PySpark or Scala-Spark in a dedicated 45-to-60 minute round. Companies on Snowflake or BigQuery without Spark in production (Stripe, Block, Coinbase) generally skip the Spark round. Check the company-specific list for the round shape at your target.

How is the data modeling round graded if there is no 'correct' answer?

The rubric scores grain selection (did you state 'one row per X' before drawing), SCD type choice with justification (Type 1 vs Type 2 vs Type 3, why), dimension shape (conformed dimensions across fact tables), and trade-off articulation (why star over snowflake or OBT, why this grain). The interviewer accepts multiple valid designs; the score comes from defense, not from picking the canonical answer.

What is the format of the pipeline architecture round?

A concrete scenario (e.g. 40 million clickstream events per day, 15-minute dashboard freshness SLA, downstream BI tool that cannot handle table swaps), 45 to 60 minutes, end-to-end design on a whiteboard or canvas. The rubric weights SLA match, cost reasoning, failure modes (what happens when Kafka brokers fail, when the source schema changes, when a partition is late), tool fit (why Kafka here and not S3 with notifications), and mid-round adapt-on-fly when the interviewer flips a requirement.

Should I prep for behavioral rounds too?

Yes. Behavioral rounds appear in every loop and account for the hire/no-hire decision when technical rounds split. Use STAR-D format (Situation, Task, Action, Result, Decision postmortem). Specific numbers required (latency, dollars, hours, downstream consumers). The decision postmortem (what you would do differently and why) is the senior-vs-mid signal.

How many problems should a data engineer solve before a FAANG onsite?

Roughly 150 problems for FAANG-level loops, distributed across rounds: 60 SQL, 40 Python, 20 modeling whiteboards, 20 pipeline designs, 10 PySpark if Spark-first. Plus 3 timed mocks in the final 2 weeks. The bottleneck most candidates hit is not volume; it is narration: thinking out loud under pressure without going silent for 2 minutes.

1,400+ Data Engineer Interview Questions, 5 Rounds

Data Engineer Interview Questions

Live-executed practice problems and rubric-scored design problems covering every round of the data engineer interview loop.

1,400+ data engineer interview questions covering all 5 rounds of a typical loop: SQL (95% of loops), Python (70%), data modeling (55%), pipeline architecture (52% of senior-and-above), and PySpark (30% at Spark-first companies). Every coding problem runs against a real grader; every modeling and design problem ships with a rubric-scored verdict.

A typical data engineer interview loop in 2026 has 5 rounds. SQL appears in 95 percent of loops as a 30-to-45 minute coding round on a Postgres-flavored editor, with patterns like top-N per group, dedup latest, sessionization, gap-and-island, SCD2 half-open joins, and idempotent MERGE. Python appears in 70 percent of loops as a 30-to-45 minute coding round on a sandbox, usually vanilla Python with pandas at most companies and polars at the leading edge. Data modeling appears in 55 percent of loops as a 45-minute whiteboard exercise on a marketplace, rideshare, payments ledger, or content platform domain. Pipeline architecture or system design appears in 52 percent of senior-and-above loops as a 45-to-60 minute end-to-end design with a concrete scenario (10 million events per day, 15-minute freshness SLA, downstream BI tool that cannot handle table swaps). PySpark appears in 30 percent of loops at Spark-first companies (Databricks, Netflix, Uber, Airbnb, DoorDash, Spotify) as a 45-to-60 minute coding round emphasizing DataFrame fluency, join strategy selection, skew diagnosis, and Spark UI reading.

What loses points across all 5 rounds is rarely syntax. In SQL it is a missed NULL case, a wrong grain, or a window definition that ties when the interviewer wanted a strict order. In Python it is catching bare Exception, not validating record-level errors, defaulting to O(n-squared) when a dict lookup is O(1). In modeling it is failing to state the grain in one sentence before drawing, or over-normalizing instead of picking a star with conformed dimensions. In design it is whiteboarding the right architecture without naming durability, replay, idempotency, and what happens when the upstream dies on a holiday. In Spark it is ignoring skew, broadcasting a table that will not fit in driver memory, or failing to read a Spark UI screenshot showing stage time imbalance.

Rubric weights are calibrated to data engineer interview write-ups from Meta, Amazon, Google, Netflix, Stripe, Databricks, Snowflake, Airbnb, Uber, DoorDash, and Pinterest. Mid-level (L4) rubrics weight correctness and clean code. Senior (L5) rubrics weight trade-off articulation and failure-mode naming (3 failure modes per component in design rounds). Staff (L6) rubrics weight adapt-on-the-fly behavior when the interviewer changes a requirement mid-round. The catalog is filterable down to seniority and to specific companies once you know your target.

Entry-level data engineer interview questions - The junior loop: SQL fundamentals, Python basics, and the first behavioral round.
SQL interview questions (95% of loops) - 931 problems with 10-seed Postgres grading for the highest-frequency data engineer round.
Python interview questions for data engineers - 412 pipeline-shaped problems with hidden test cases for the data engineer Python round.
Data modeling interview questions - Star schemas, SCD types, medallion, with rubric-scored verdicts.
Pipeline architecture interview questions - Clickstream, CDC, reconciliation, ML feature store designs with failure-mode rubrics.
PySpark interview problems - Join strategy, skew diagnosis, Spark UI reading at Spark-first companies.
Data engineer system design interview prep - End-to-end design rounds with SLA + cost + failure mode rubrics.
ETL design interview prep - Idempotent ETL, MERGE strategies, schema evolution, late-arriving data.
Senior data engineer interview problems - L5 and L6 rubrics emphasizing trade-off articulation and mid-round pivots.
FAANG data engineer interview problems - Meta, Amazon, Google, Netflix, Apple-tagged problems with per-company rubrics.
Data engineer interview questions with worked answers - Worked solutions for the 4 rounds with the why behind each answer.

How many rounds does a data engineer interview loop have?: 5 typical rounds: SQL (95 percent of loops), Python (70 percent), data modeling (55 percent), pipeline architecture or system design (52 percent of senior-and-above loops), and PySpark (30 percent at Spark-first companies). Phone screens are usually SQL plus a take-home or a 60-minute design walkthrough. Onsites add the remaining rounds plus a behavioral round.
What is the difference between a mid-level and senior data engineer loop?: Mid-level (L4) loops weight correctness and clean code: did you produce a working solution that handles the obvious edge cases. Senior (L5) loops weight trade-off articulation and failure-mode naming: did you name 2 alternatives, defend the choice, and call out what happens when the upstream dies on a holiday. Staff (L6) loops weight adapt-on-the-fly behavior: when the interviewer changes the SLA from 15-minute freshness to 1-minute mid-round, did you pivot cleanly.
Do all data engineer interviews include a Spark round?: No. Spark-first companies (Databricks, Netflix, Uber, Airbnb, DoorDash, Spotify) test PySpark or Scala-Spark in a dedicated 45-to-60 minute round. Companies on Snowflake or BigQuery without Spark in production (Stripe, Block, Coinbase) generally skip the Spark round. Check the company-specific list for the round shape at your target.
How is the data modeling round graded if there is no 'correct' answer?: The rubric scores grain selection (did you state 'one row per X' before drawing), SCD type choice with justification (Type 1 vs Type 2 vs Type 3, why), dimension shape (conformed dimensions across fact tables), and trade-off articulation (why star over snowflake or OBT, why this grain). The interviewer accepts multiple valid designs; the score comes from defense, not from picking the canonical answer.
What is the format of the pipeline architecture round?: A concrete scenario (e.g. 40 million clickstream events per day, 15-minute dashboard freshness SLA, downstream BI tool that cannot handle table swaps), 45 to 60 minutes, end-to-end design on a whiteboard or canvas. The rubric weights SLA match, cost reasoning, failure modes (what happens when Kafka brokers fail, when the source schema changes, when a partition is late), tool fit (why Kafka here and not S3 with notifications), and mid-round adapt-on-fly when the interviewer flips a requirement.
Should I prep for behavioral rounds too?: Yes. Behavioral rounds appear in every loop and account for the hire/no-hire decision when technical rounds split. Use STAR-D format (Situation, Task, Action, Result, Decision postmortem). Specific numbers required (latency, dollars, hours, downstream consumers). The decision postmortem (what you would do differently and why) is the senior-vs-mid signal.
How many problems should a data engineer solve before a FAANG onsite?: Roughly 150 problems for FAANG-level loops, distributed across rounds: 60 SQL, 40 Python, 20 modeling whiteboards, 20 pipeline designs, 10 PySpark if Spark-first. Plus 3 timed mocks in the final 2 weeks. The bottleneck most candidates hit is not volume; it is narration: thinking out loud under pressure without going silent for 2 minutes.

1550 practice problems matching this filter. Domains: SQL (931), Pipeline Architecture (144), Data Modeling (63), Python (412). Difficulty: medium (741), hard (265), easy (544).

SQL (931)

10 Lowest Uptime Services - medium - Ten services at the bottom of the reliability chart.
Proof of Presence - medium - Two-factor sent. How many confirmed?
2nd Most Common Content Type - hard - Everyone talks about number one. What about number three?
30-Day Page View Counts - easy - Thirty days of engagement. Quick snapshot.
7-Check Rolling Average - medium - Seven entries hold the trend.
7-Day Onboarding Conversion - hard - Signed up Monday. Still here by Sunday?
7-Day Token Retention - medium - Premium tokens, day by day.
80th Percentile API Latency - medium - The 80th percentile tells the real story.
90th Pctl Model Accuracy Gap - medium - Most models are fine. The bottom 10% are not.
Above Average - easy - Products beating the catalog average.
Where the Money Burns - medium - Some services quietly burn more than the rest.
Above Average Interactions - easy - The average user is boring. Who is above?
Above Average Product Prices - medium - Some products cost more than they should.
Above Category Average - easy - The category average is one thing. These beat it.
The Above Average - medium - What counts as good depends on the company you keep.
Above the Curve - medium - Spenders who break from the pack.
Above Their Station - medium - Sometimes the report out-earns the boss. Find where the ladder bends.
Active API Tokens - easy - Tokens that have actually been used.
Active Campaigns - easy - Which campaigns are earning their keep?
Active Duo - medium - Shoppers who also browse. The overlap is the insight.
Turned Away - medium - Every gate keeps a record of who it stopped.
Active Tokens on Target Date - medium - One specific day. Which tokens were still alive?
Active User Open Rate - medium - What share of push notifications were opened by active users
Active User Penetration Rate - hard - How much of the user base is actually alive?
Active User Revenue for April - easy - Total revenue from active users in a single month
Beyond the Signup - medium - Anyone can create an account. Fewer actually return.
Active Users With April Transactions - easy - Active accounts that also opened their wallets. How many?
Presence vs. Participation - medium - Being in the region and being active are two very different things.
Activity Histogram - easy - How many users did X things? Build the distribution.
Ad Clickers - easy - Who clicked? What did they spend?
Adopters Before Migration - hard - They used the old feature. Did they ever touch the new one?
Ad Revenue 2026 - easy - Annual ad revenue. On the books.
Ad Revenue by Age Bucket - medium - Ad dollars, sliced by country.
After Hours API Calls - medium - The office is dark. The API is not.
The Vote Tally - hard - One product, every day it sold, and the money it brought in.
Alert Count by Severity Tier - medium - Alerts by severity. The breakdown matters.
Alert Hotspots by Service and Severity - easy - Some services and severities light up more than others.
Alert Response Breakdown - medium - An on-call postmortem asks which services are bleeding alerts nobody acknowledges.
Alert Severity - hard - When the alarms go off, who screams loudest?
The Severity Matrix - medium - When services cry wolf, the numbers reveal who's serious.
All Infra Regions - easy - The infrastructure spans the globe. Map it.
All Known Endpoints - medium - Two tables. One truth. Every endpoint accounted for.
Allocations in Top Spending Region - hard - The biggest spenders live in one region.
The Tag Order - hard - Tags arrived in chaos. The system needs them in line.
Annual Cloud Spend - easy - One year of cloud bills. The total.
Annual Cloud Spend Summary - easy - A year of cloud bills. Add it all up.
Annual Pipeline Failures - easy - How many pipelines broke this year?
API Call Distribution Fraction - hard - Not all endpoints are created equal.
API Calls With and Without Errors - medium - Some calls succeed. Some do not. Break it down.
Echo Chamber - medium - Same status, same pattern. Coincidence?
API Token Churn Rate - medium - Tokens come and go. What's the turnover?
API Traffic by CDN Edge - medium - CDN paths carrying API traffic. Which edges?
App Stability by Region - medium - Some regions crash more than others.
April and May Active Users - easy - Spring cleaning for the user base. Who was actually around?
Accounted For - medium - Every impression is a face in the crowd; some we can name, the rest are strangers. Measure the gap, campaign by campaign.
Auction Lot Summary - medium - The hammer falls. Who bid the most?
Auth Endpoint Callers - medium - Identify users who have called authentication API endpoints
Auth Endpoints - easy - Not all endpoints are visible to everyone.
Authors Deploying to Dev and Production - medium - Dev, staging, production. Who has touched all three?
Authors With Successful Deploys - easy - Who deployed successfully?
Auth Service Health Checks - easy - One service. Full audit trail.
Average Accuracy by Framework - medium - Not all frameworks deliver the same accuracy.
Average API Latency by Year - medium - Latency year over year. Is it getting better?
Return on a Glance - easy - Every impression costs something. Find the campaigns earning it back.
Average Build Duration by Repo - easy - Some repos build fast. Others don't.
Average Compensation by Department and Status - medium - Average compensation. Department by department.
Average DQ Fail Rate - easy - Average failure rate, table by table.
Average Event Progression Time - hard - How fast do users move through the funnel?
Average Fulfillment Lag - medium - Ordered, then... waiting.
Average GPU Node CPU Usage - easy - GPU nodes burning CPU. How much?
Metric Trend by Department - easy - How each team's numbers moved, year over year.
Average High-Range Accuracy - easy - The top-scoring models. What's their average?
First Contact - medium - Every user's first hello to an endpoint. Timed.
Under the Same Name - easy - The same state wears different casing. Read the latency behind each one.
Average Latency by Status - easy - Each status code has its own latency story.
Average Node CPU by Region - easy - Average infrastructure node CPU usage broken down by region
Average Node Utilization - easy - CPU and memory, region by region.
Average Rating by Category - easy - Category ratings. Some shine, some don't.
Average Response Time by Hour - easy - Hour by hour. When does latency spike?
Average Results for Python Searches - medium - Python searches. What's the click-through?
Average Review Comments by Author - medium - Some authors get more feedback than others.
Average Search Endpoint Latency - easy - One endpoint. Average speed.
Average Search Results Per User - easy - How many results per searcher?
Average Session Duration - medium - How long do users actually stay?
Average Session Duration by Device - easy - Session length, device by device.
Average Sessions Per User - hard - How often do users come back?
Average Spending by Account Status - medium - Average per-user lifetime spending segmented by account status
After the Handshake - medium - The first call is a promise. Judge the ones that follow.
Average Watch Time by Format - medium - Which content format keeps viewers watching the longest
Not All Fires Are Equal - medium - The alert volume varies. So does what it means.
Who's Holding Up Traffic - medium - Some endpoints carry the product. Others are barely touched.
The Ones Who Hold Attention - medium - Time on screen is the real vote. Find the creators earning it.
Bargain Bin - easy - Floor prices. Right before the vendor call.
Bargains and Budget-Busters - hard - Every region has both. Find them.
Batch Job Performance Tiers - medium - Every batch job gets a grade.
Best Accuracy to Training Time Ratio - medium - Fast to train. Accurate too. Which model?
Best Day for Ad Revenue - medium - Some days of the month convert far better than others.
Best in Class - medium - Every category crowns exactly one earner. Find who wears it.
Kings of the Calendar - hard - Every month has a winner.
The Heavy Hitters - easy - Total sales tell the real story. Surface the products that carry the catalog.
Biggest Deployment Decline - medium - One team's deploy count cratered. Which one?
Big Spenders - easy - The whale list.
The Switchboard - medium - On or off. Every flag at a glance.
Bottom 2% Services by Spend - hard - The bottom 2% of spenders. Who are they?
The Ones Nobody Calls - medium - The POST paths the traffic forgot.
Bronze Medal - easy - Only the top few clear the bar.
The Budget Line - easy - Some rows are over. Some are under. Label every one.
Budget-Friendly Products - easy - Affordable does not mean invisible.
Build a dynamic report header - medium
Build Health - medium - Rank every repo by how often CI stays green.
Builds per Author per Branch - medium - Who triggered what, and where?
Build Success Rate by Trigger - medium - Which triggers produce green builds?
Build Success vs Failure by Repo - medium - Green versus red, repo by repo.
Busiest Pipeline Month - medium - One month, more pipeline runs than any other.
The Loudest Rooms - medium - Every channel has an audience. Find where it is biggest.
Busy Authors - medium - Some developers spread their commits everywhere.
Cache Efficiency - hard - Some edges run hot. Others coast on the global average.
Calculate the median transaction amount (50th percentile) and the 95th percentile transaction amount - medium
Campaign Bookend Engagement - hard - First impression versus last. The gap.
Campaign Click-Through Rates - medium - Clicks per impression. Campaign by campaign.
The Notification That Paid Off - hard - The message went out to thousands. A smaller number actually bit.
Campaign Conversion Window - hard - A narrow window between impression and action.
Campaign Cost Effectiveness - medium - Money in, conversions out. What is the ratio?
Losing Altitude - hard - Two months apart, the same campaigns. Find the ones that slipped.
Two Names, One Campaign - easy - The ad team and the push team never agreed on naming. Find where they secretly meant the same thing.
Click-Through by Campaign - medium - Which campaigns actually got the tap.
Campaign Revenue Totals - easy - Every campaign has a price tag. Total them up.
Campaigns With Most Clicks - medium - The campaigns getting all the clicks.
Cart Sizes - easy - Power buyers. Big carts.
Categories With Mixed Price Tiers - medium - Users who cross content types.
Category Buyers - medium - Which categories have the broadest reach?
Category Census - easy - Which aisles are worth restocking?
Category Deep Dive - hard - Revenue, units, rank. The full category report card.
Category Revenue - medium - Which categories pull their weight?
Category Sales Summary - easy - Category by category. How did they do?
Category-Specific Product Volume - easy - Sum transactions for a specific payment type.
CDN Image Request Paths - easy - CDN image traffic. Every path.
CDN-Related DNS Lookups - easy - DNS lookups tied to the CDN.
CDN Traffic by Day and Hour - medium - CDN traffic, hour by hour.
Character Position in Endpoint - easy - URL patterns, character by character.
Chat Activity - easy - Which channels are ghost towns?
Cheapest CDN Route - easy - The cheapest path across regions.
Cheapest Cost Per Region - easy - Lowest spend per region.
Cheapest High-Rated Product - medium - Cheap and highly rated. A rare combination.
Cheapest Transaction per User - easy - Everyone has a smallest purchase.
The Quiet Outlier - hard - Ignore what the traffic does all day. Find the spike that barely showed up.
Name Recognition - medium - The name tells you what it is. Mostly.
Clean Averages - easy - Merchandising only cares about the categories customers actually rate.
Clean Cache CDN Edges - easy - Cached, clean, error-free edges.
The Silent Probe - easy - One probe never recorded. The rest still need reporting.
Clicked Ad Impressions - easy - They saw the ad. They clicked.
Loyalty's Double Tap - medium - When a nudge and a banner team up.
Break Through - medium - A click is the only vote that counts.
Click Revenue - easy - Which campaigns are earning their keep?
Diminishing Returns - medium - When search comes back thin, does the click still follow?
Cloud Bill - easy - Which cost buckets are bleeding money?
Cloud Cost Breakdown by Provider - hard - Cloud costs, provider by provider.
Cloud Cost by Team - easy - Spend by team. Who's burning most?
Cloud Cost Stats by Provider - medium - Three providers. Three very different bills.
Cloud Cost Trend Analysis - medium - Cost trends across billing periods.
Combined Cloud Spend by Region and Service - medium - Region by region. Service by service. Where does the money go?
Commit Cadence - hard - Some repos go quiet for too long.
Commit Royalty - medium - In a sea of commits, only a few wear the crown.
Common Age Buckets - easy - Duplicate records hiding in the users table.
Clean Exit - easy - Priority one. Only some of them made it to the end.
Completion Rate - medium - Not every region closes orders cleanly. The percentages tell the story.
Compute Nodes in Key Regions - easy - Compute nodes across the key regions.
Consecutive Cost Growth Periods - hard - Five straight months of spending increases.
Consistent High-Quantity Revenue - medium - Big orders, consistent revenue. A rare combination.
Content by Specific Users - easy - Two creators. What did they publish?
Content Duration Snapshot - easy - A popularity snapshot by duration.
Content Mix - easy - One content format to bet the quarter on.
Content Page Spreads - hard - Content, laid out in two columns.
Content Published in 2026 - easy - Published back then. Still relevant?
The Blind Spot - medium - Pages they haven't discovered yet.
Content Session Counts - medium - Session metrics, content item by item.
Content Sorted by Duration - easy - The catalog, sorted by length.
Content Type Distribution - easy - How many of each content type?
Content Types by Creator - easy - One creator. What did they make?
Content Viewer Penetration - easy - What share of the user base has viewed at least one piece of content
Cost Density Extremes - medium - Some regions pack more cost per node than others.
Cost Efficiency Ratio - easy - Dollars in, value out. What's the ratio?
Cost Efficiency Variance - hard - Cost efficiency varies. By how much?
Cost Share Within Category - medium - Each entry's slice of the category total.
Service Roll Call - easy - The mesh is sprawling. Find out exactly how many services are actually running.
Regional Footprint - easy - Every node costs money. Know what you own.
CPU Utilization Summary - easy - The CPUs are working. How hard?
Creator Favorite Content Type - hard - Every creator has a go-to format.
The Long Watch - medium - Some formats hold you longer than others. Measure which ones.
Parallel Traces - medium - Same experiment. Different variants. Who overlaps?
The Slow Build - medium - Month over month, the number grows. Track how the average moves with it.
Cumulative Sales Per Customer - medium - Each purchase adds to the running total. Watch it climb.
Live Wire - medium - The last switch each team flipped.
Customer Full Name Concat - easy - First name, last name. Combine them.
Customers Without Orders - medium - Customers who have never ordered.
Custom Message Type Counts - medium - Not all messages are created equal.
Daily and Weekly Active Users - easy - One metric by day, one by week. Same users, different lenses.
Daily Cross-Platform Users - easy - Mobile and web. Same day, same users?
Ship It or Skip It - easy - The calendar doesn't lie. How aggressive is this team, really?
Daily Error Count Change - medium - Errors, trending up or down?
Daily Error Resolution Ratio - medium - Reported versus removed. The daily ratio.
Deploy Velocity Swings - medium - Month to month, who sped up and who stalled.
Daily Net Revenue - hard - Net revenue, day by day. Refunds included.
Daily Session and User Counts - medium - Sessions and users, day by day.
Campaign Click Rate - medium - Among engaged users, which campaigns landed.
Loudest in the Room - medium - Every day, a few endpoints carry the load. Surface them.
The Undone - hard - Some migrations don't stick. Find the databases where they keep coming undone.
Data Repo Fix Commits - medium - How many commits start with 'fix'?
Days with More Edited Than Unedited Messages - medium - Some days, more messages get edited than sent.
The Freshest Record - medium - Duplicates everywhere. Only the most recent version of the truth survives.
The Clean Aisle Numbers - medium - Clear the noise. What did each category actually earn?
Department Cost by Status - medium - Headcount and compensation. The dashboard view.
The Org Chart in Numbers - hard - Headcount by department, sliced by quarter. Every seat accounted for.
Department Running Totals - medium - Compute cumulative metric values within each department using window operations.
Department Snapshot - medium - Who is underperforming and who is excelling?
Department Spend Difference - easy - The compensation gap between departments.
Department Spend Gap - easy - Gap between Engineering's and Marketing's biggest single purchase
Deploy Author Performance Score - medium - Not all deployers are equally reliable.
Deploy Cadence - easy - Which environments ship the most?
Deploy Count by Service - easy - Some services deploy constantly. Others barely at all.
Deployed Models by Framework - easy - Which frameworks are actually in production?
Deployment Duration by Status - easy - Fast deploys versus slow ones. By outcome.
Deployment Failure Impact - medium - When deploys fail, how bad is the blast radius?
Deployments per Environment - medium - Dev, staging, prod. Where do most deploys land?
Deployments Without Alerts - easy - Deployed without a single alert. Suspicious or impressive?
Deploy Reliability Scores - medium - A reliability scoreboard for deploy teams.
Deploy Velocity - hard - Days between deploys. Some services ship fast, others crawl.
The Apprentices Still in the Forge - easy - A model is not a model until it stops learning and starts earning.
Device Mix - easy - The device breakdown before the redesign.
Devices Per Age Bucket - medium - Device diversity among the younger users.
Device Type Serving Most Users - medium - One device type serves more users than the rest.
Device Types With Chrome Users - easy - Power users and their devices.
Disabled Feature Flags - easy - Disabled flags. Still worth auditing.
Disabled-Flag Share by Owner - medium - Which teams ship everything off by default.
Distinct Blog Referrers - easy - Where did the traffic really come from? No repeats.
Two-Way Street - medium - A conversation reads the same from either side.
Distinct Product Categories - easy - A quick category inventory.
Diverse Shoppers - medium - They shop the whole catalog.
DQ Fail Rate by Table - medium - Pass rates, table by table.
DQ Score Spread - medium - The spread in data quality scores.
Double Take - medium - Passed QA twice. That's the problem.
Duplicated User Event Messages - medium - Duplicated messages from the alerts topic.
Duplicate Training Runs - medium - Same model, trained twice.
Early Commit Velocity by Author - medium - How productive was each author during the first year of a repo's CI pipeline
Early 2026 Data Pipelines - easy - Which pipelines ran before the year turned mid.
Early User Activation - medium - Activated early. A good sign.
The Fast Lane - medium - Only the quick runs make the cut. Measure what they move.
Email Census - easy - The reachability split.
The Roster - easy - Every department, counted head by head.
Endpoint Latency Spread - medium - Latency spread across endpoints.
Verbose by Design - hard - Some paths say in six segments what others say in two.
Endpoint Performance Report - medium - Every endpoint has a speed and a reliability story.
Endpoint Ranking - hard - The slowest endpoints. Called to the principal's office.
Endpoint With Most GET-Only Users - medium - Read-only users have a favorite endpoint.
Engagement by Content Type - medium - Some content types get all the attention.
Engagement Gap - medium - Zero transactions is still a data point. Count everyone.
Error Category Breakdown - hard - Postmortem time. Categorize the errors.
Error Hall of Fame - medium - The year's worst error categories.
Fault Lines - medium - Errors by day and region. Some areas are worse than they appear.
Error Severity Buckets - easy - Errors sorted by how much they hurt.
Errors With Service Health - easy - Error data, enriched with health context.
Even-ID February Signups - easy - A very specific slice of a very specific cohort.
Even-ID June Signups - easy - Odd IDs, even IDs. The filter is precise.
Event Count on Key Days - easy - Key days. Key event volumes.
Events by Month Across Years - easy - Month by month, year by year. The pattern emerges.
Event Types Spanning Multiple Months - easy - Some events span seasons.
The Ones Worth Paging - hard - Three levels wake someone up at night. Tally each one.
Exclusive Users per Device Type - medium - Loyal to one platform only.
The Quiet Drain - easy - Some AWS services quietly drain the budget.
The A/B Verdict - medium - Variant A or Variant B. The conversion numbers pick the winner.
Experiment Impact - hard - Which experiments moved the needle? Settle the standings inside every variant.
Balance of Arms - hard - Every test has two sides. Count who actually landed on each.
Extract Deploy Versions - medium - The version number is buried in the log.
Extreme API Token Usage - medium - Outlier tokens. Suspiciously busy.
Extreme Category Totals - medium - The highest and the lowest. Both are interesting.
Extreme Headcount Departments - easy - The pay extremes tell a story.
Extremely Late Resolutions - medium - Twenty minutes past the SLA. Still unresolved.
Broken Promises Between Tables - medium - Every foreign key is a pinky-swear. Count the ones that got broken.
Rollback Roulette - easy - Some ships sink before they leave the harbor.
Failure Rate - medium - Build failures happen. Which repos break the most?
The High and the Low - hard - The fastest and slowest in every region.
Fastest CI Build Date - medium - The fastest build ever. When did it happen?
Fastest Completion Per Day - medium - Every day has a speed champion.
Fastest Page View to Click - hard - How fast from view to click?
Fastest Regions by Latency - medium - The fastest regions. Benchmarked.
Feature Flag Adoption - medium - How widely adopted are the flags?
Feature Flag Engagement Impact - hard - Flags on versus flags off. The engagement gap.
Feature Flag Fan vs Detractor Pairs - hard - Some users love the flag. Others want it gone.
Feature Name Intersection - hard - Training names versus serving names. The overlap.
Feature Quality by Source - medium - Quality varies by source.
Features With Missing Values - easy - Missing data in the features.
Feature Vote Winner - medium - Users voted with their clicks. Who won?
February 2024 Signups - easy - One signup window. One cohort. Who joined the club?
Not From Around Here - easy - The data is mixed. Only some of it belongs.
Filtered User Roster - easy - A clean roster for the all-hands.
Find active users in the '25-34' age bucket - medium
Find all products with a price between 20 and 80 (inclusive) - medium
Find all products with a price greater than 25 - medium
Find Deploy Authors - easy - Same person. Many different spellings.
Find the Fifth Largest Cost - medium - Not the biggest. Not the smallest. The fifth.
Find transactions over $100 with quantity greater than 2 - medium
Find users whose age_bucket is '18-24', '25-34', or '35-44' - medium
First and Last Peak Accuracy Dates - medium - Peak accuracy. When it first hit and when it last did.
First and Last Timeout Per Service - medium - First timeout. Last timeout. Each service.
First Build per Repository - easy - Every repo had a first build.
The Ninety-Day Comeback - hard - Everyone shows up once. Who comes back before the quarter ends?
First Deploy Attribution - medium - The first deploy per service.
First Half of Page Views - medium - Half the data. The first half.
First Interaction Credit - hard - Attribute transactions to earliest touchpoint
First Migration Record - easy - The very first migration. Where it all began.
First Contact - easy - Every pipeline has a first run. This is what it brought back.
First Time Learners Per Day - medium - Brand new users, day by day.
First Touch Attribution - medium - The first interaction matters most. Or does it?
Flag Check - easy - Which flags are actually live?
Chain of Command - hard - The tree runs deep. Trace every branch back to the top.
Follow the Money - easy - Every dollar leaves a trail. Find the accounts moving the most of it.
Frequent Message Senders - medium - Someone is sending too many messages.
The Company You Keep - medium - Only experiments with a crowd count. Find the Friday sessions they drove.
Friday Spending Analysis - hard - Friday spending during Q1.
Did We Actually Make Money? - medium - Cancelled deals don't count. The rest shows where the money really came from.
Roll Call - easy - Every name on the books, in order.
Full Funnel - hard - Search. Browse. Buy. Only a few do all three.
The Weight of a Click - hard - Where users actually spend their attention.
Gateway Connection Timeouts - easy - Timeouts at the gateway.
Ghost Products - medium - Listed but never sold. The shelves collect dust.
Health Check Distribution - easy - Pass, fail, degraded. The distribution.
Health Checks per Service - easy - Some services get checked constantly.
Healthiest Service Check History - hard - The healthiest service. Full history.
Heavy Ad Exposure - medium - Saturated with ads. Is it too much?
Heavy Hitters - medium - Some repos never sleep.
Heavy Namespaces - medium - Kubernetes has favorites. Some namespaces carry more weight.
Repeat Offenders of the Search Bar - easy - Once is a fluke. Twice is a habit.
The Ones That Woke Us - easy - The year's serious incidents, and nothing quieter.
High Engagement Pages - hard - Some pages hold attention longer than others.
Higher Performing Variant - easy - Control versus treatment. One wins.
Higher Than Supervisor - easy - When the student outscores the teacher.
Highest and Lowest Cloud Costs - medium - The extremes in cloud spending.
Highest Cost Per Team - easy - Peak cost, team by team.
Highest Daily Spend - medium - Somewhere in that window, someone broke the spending record.
Highest Latency Endpoints - easy - The slowest endpoints. Everyone notices.
Hottest Regions by CPU - medium - Where the fleet runs warmest.
Highest Throughput Pipelines - medium - The pipes that carry the most water.
High-Output Creators - easy - High engagement creators.
High Price Products - easy - Everything above 100.
High-Rated In-Stock Percentage - easy - Highly rated and in stock. A rare combo.
High-Spend 2025 Campaigns - easy - Big-budget campaigns from last year.
High-Traffic Endpoints in February - easy - When traffic spikes, some endpoints get buried. How many crossed the line?
High-Value Electronics - easy - The five priciest electronics.
High Volume Batch Jobs - easy - Batch jobs that processed millions.
Holiday Promo Campaign Click Year - easy - One year, the holiday campaign exploded.
Holiday Sale Campaign Revenue - easy - The holiday sale campaign. How did it do?
Idle Team Members - easy - Sprint started. Some people never got assigned.
Impressions by Search Keyword - hard - Campaign performance, keyword by keyword.
Radio Silence - medium - Android control cohort. Gone quiet.
Inactive Unverified Users - easy - Signed up. Never verified. Never came back.
Inactive Users in Date Range - medium - Ghost accounts. Active signup, zero sessions.
Inactive vs Suspended Engagement - medium - Premium versus free. The engagement gap.
Incident Keyword Messages - hard - Certain words trigger an investigation.
What's in a Name - easy - Group by the first letter, count the heads, show the share.
Actually Available - easy - The catalog is big. The shelf is smaller.
Intra-Region Latency Diff - hard - Same region. Different latency.
The Upgrade Divide - medium - The install numbers don't match the hype.
iOS Sessions by Device Type - medium - iOS engagement, device by device.
Japan Revenue for April - easy - Last month's numbers for one region.
Job Status Duration - medium - How long in each job state?
The Full Picture - easy - Two tables know different things about the same people. Combine them.
The Row Count Surprise - easy - Same tables. Different handshakes. Wildly different results.
Keep Most Recent Record - medium - Carbon copies clutter the table. Only the latest matters.
Keyword-Based User Search - medium - The search terms reveal intent.
Largest A/B Test by Participants - medium - The biggest experiment ever run.
Largest CDN Response - hard - One edge location served something massive.
Largest Group - easy - One group towers above the rest.
Largest Single Cloud Cost - medium - One line item. The biggest bill of all.
The Last Checkout - medium - Their last visit. Everything in the bag.
Last Five Batch Jobs - easy - The last five. A quick tail check.
Last Migration Record - easy - The most recent migration. Is it the last?
Last Server Activity - easy - Each server's last heartbeat.
Latency Gap to 10th Fastest - medium - One server. Compared to the 10th fastest.
Latency Quartiles Per Endpoint - hard - Quartile breakdowns. Endpoint by endpoint.
Latency Variance and Std Dev - hard - How much does latency actually vary?
Latency vs Regional Average - easy - Each service versus its region's average.
Latest Commit Build Cost - medium - The latest commit came with a build cost.
Latest Metric Values - easy - Stale records hiding in the metrics.
Latest Migration Output per Author - medium - Each author's most recent migration output.
Latest Session Per User - easy - Everyone has a most recent session.
Latest Version Per Service - easy - The latest version deployed. Each service.
Leading ML Frameworks by Accuracy - medium - Which frameworks lead on accuracy?
Least Viewed Content - medium - Nobody is watching. Should it still exist?
Log Entries by Level - easy - Info, warn, error, fatal. The breakdown matters.
Log Levels - easy - Severity breakdown with response times.
Log Priority - easy - Which servers are on fire before coffee?
Log Volume by Day of Week - easy - Some days are noisier than others.
Longest Active Membership Streak - easy - The longest unbroken streak.
Longest Deploy With Full Identifier - easy - The longest deployment. Full ID.
Longest Gap Between Token Events - medium - The longest gap between token events.
Longest Running Pipeline - medium - One pipeline outlasted them all.
Longest Uptime Streak - hard - Pass, pass, pass. How long until fail?
Longest Visit Streaks - hard - Day after day after day. Who kept coming back?
Long Messages - medium - Some commit messages tell a novel.
Long-Running Feature Flags - medium - Flags that have been on for too long.
Long Searches Containing 'er' - easy - Long queries with 'er'. A pattern?
Low-Byte CDN Responses - easy - Tiny responses from the edge.
Low-Engagement Sessions - medium - Users whose average session duration is below the engagement threshold
On Their Way Out - easy - They signed up. They never really showed up.
Lowest Average Price Category - easy - The cheapest category. Not necessarily the worst.
Cheapest Line for Network-Heavy Teams - medium - Among the network spenders, the smallest single line.
Lowest CPU Pods per Namespace - hard - The five lightest pods per namespace.
Lowest Latency per Service - medium - The fastest response each service ever gave.
Low Latency API Calls - easy - Fast endpoints. Confirmed fast.
Low Severity Checks in 2026 - medium - Low severity. High volume.
Low Severity DQ Checks - easy - Low severity checks. All of them.
Low Throughput Pipelines - easy - Pipelines barely moving data.
Low Uptime Services - easy - Underperforming services.
Low-Volume Stream Topics - medium - Quiet topics in the stream.
March Revenue by Customer - medium - One month, every customer, every dollar accounted for.
Market Share - hard - Every category wants a bigger slice.
Max Value Per Location - easy - Every location has a peak.
Active Token Owners in 2026 - easy - Active token owners this year.
Median Cloud Cost by Service - hard - The median cloud bill, service by service.
Median Failure Rate by Table - hard - Half the tables fail more than this.
Below the Peaks - hard - The biggest bills catch every eye. The overspend hiding just beneath them does not.
Median Model Accuracy - hard - The median accuracy. Not the mean.
Median Null Percentage of Float Features - medium - Nulls in float columns. How widespread?
Median Transaction by Category - hard - The middle transaction in each category.
Memory-Heavy Pods - easy - Memory-hungry workloads.
Mentorship User Pairs - medium - Pair them up. Mentor and mentee.
What Set It Off - easy - Every build has a cause. Tally the work behind each one.
The Weight of Words - easy - Verbose commits. Risky changes?
Messages Containing Keyword - easy - Flagged terms in the messages.
Messages From Specific Users - easy - Specific users. What did they say?
Metric Range by Department - medium - Where each team's numbers sit, low to high.
Metric Range Per Group - easy - The spread within each group.
Metric Value Pairs Over Threshold - medium - Two metrics, both above the line.
Metric Value Quarter Complement - easy - Two metrics that accidentally match.
Metric Volatility Gap - easy - Stable metrics are boring. Volatile ones need attention.
Mid-CPU Nodes - easy - Not the heaviest. Not the lightest. The middle.
Mid-Range Cost Allocations - easy - Not the cheapest. Not the priciest. The middle.
The Comfortable Middle - hard - Above average but not extreme.
The Quiet Middle - easy - Not the biggest, not the smallest. The overlooked middle.
The Floor Price - medium - Before the negotiation, find what each provider really charges at its cheapest.
Minimum Parallel Workers - hard - Too few workers and it stalls.
Missing Email for Non-Active Users - easy - No email on file. No recent activity. Something smells off.
Mobile Event Counts - easy - Mobile engagement, device by device.
Mobile vs Desktop Session Duration - medium - Mobile versus desktop. Who stays longer?
Then and Now - hard - Accuracy used to be higher.
Models With Variable Accuracy - medium - Accuracy should be stable. These models are not.
Model Training Completion Rate - medium - How many models finished training?
Creatures of Habit - hard - Every big team has one service it can't quit.
Monthly Active Users per Endpoint - easy - One endpoint, many users. Which ones showed up?
Monthly Category Totals - easy - Sum amounts by category and month.
Yesterday's Weather - hard - The forecast was off. By how much?
Monthly Cohort Retention - medium - Compute month over month retention rates for user signup cohorts.
Deploy Outcomes by Service - hard - Success, failure, rollback - side by side.
Thirty Days of Shipping - easy - A month in the life of an engineering team, counted one deploy at a time.
Ebb and Flow - hard - The rise and fall of revenue, one month against the last.
The Shape of the Year - medium - Revenue has a rhythm. Trace it, month by month.
Monthly Running Total - medium - Cumulative sales per product across months.
Who Stayed - hard - A footprint either holds or it slips away. Find how much stays.
Monthly Signup Counts - easy - Signups, month by month.
The Cloud Bill - medium - Every provider sent an invoice. Every month tells a different story.
The Spending Rhythm - easy - Every month tells a spending story, user by user.
Monthly Transaction Summary - medium - A monthly engagement summary.
Who We Reached - easy - Monthly reach, campaign by campaign.
Month With Fewest Deploys - medium - One month, nobody deployed.
Morning Warning Logs - easy - Warnings before noon.
Most Active Chat Users - medium - The loudest voices on the platform.
Fresh Ink - medium - Recent activity is the only activity that counts. Name the busiest hands.
The Loudest Machines - medium - Every server keeps a diary. Find the ones that never stop writing.
The Loudest Threads - medium - The code reviews that started a debate.
The Usual Suspects - easy - Export runs pile up by outcome. See which ending wins.
Most Common Monday Outcome - medium - Mondays have a pattern.
The Fast Lane - medium - Every millisecond has to earn its keep.
No Dead Months - hard - Every month it ran, it landed a click. Among those, find the ones whose worst month of spend stayed lowest.
Most Efficient Region by Token Usage - hard - Some regions squeeze more out of every token.
Most Frequent Error Types - medium - The errors that keep coming back.
First Among Equals - medium - When more than one product wears the crown, name every one of them.
What Fills the Feed - medium - Every slot in the catalog is a bet. See which format keeps winning it.
Most Popular Signup Day - medium - One day of the week wins on signups.
Most Profitable Region Month - medium - One region, one month. Peak profit.
Most Recent Token Usage - easy - Each user's latest token activity.
Across the Aisles - hard - The best customers never stay in one aisle.
The Tiebreaker - easy - One column wasn't enough. The second column settles it.
Multi-Host Regions by Node Type - medium - Some regions are quietly building empires.
Multi-Month Active Users - hard - Active this month and last month. Who stuck around?
Multi-OS Users - easy - iOS today, Android tomorrow.
Multi-Provider Cost Lookup - easy - AWS, GCP, Azure. Side by side.
The Three-Way Report - medium - Three tables. One summary. Every piece depends on the others.
Multi-Variant Experiments - easy - One user, multiple experiments.
Mutual Channel Connections - medium - Two users. What channels do they share?
The Fault Lines - medium - Some account groups hit far more errors than others. Surface the ones that break most.
Net Lines - medium - Some authors build. Others trim. The net tells the truth.
Never-Ordered Products - easy - In the catalog. Never purchased.
New Customers Per Day - medium - Count users whose first order falls on each date.
Infant Mortality - hard - The youngest ones break first.
New User Purchases - medium - What's this year's signup cohort worth so far?
New vs Returning User Share - hard - Fresh faces versus familiar ones.
Nodes by Region and Type - medium - Broken down by region. Broken down by type.
Where the Fleet Lives - medium - Six regions on the map. Where does the fleet cluster?
Nodes in Target Regions - easy - The target regions need attention.
Node Summary Per Region - easy - Every region has a node story.
Node Utilization - hard - Overloaded nodes hiding in busy regions. Spot the hot spots.
No Gaps - easy - Zero blanks. A clean contact list.
Noisiest Tables by DQ Failures - medium - The tables that fail the most checks.
Noisy Endpoints - medium - The routes generating the most noise.
Non-Bot Acknowledged Alerts - easy - Human-acknowledged alerts only.
Non-Draft Content - easy - Everything except drafts.
Non-Trivial Fatal Errors - medium - Short errors are noise. Long ones matter.
Normalization Tradeoffs in Practice - hard - Clean data or fast queries? You can't always have both.
Seen or Ignored - medium - A send is only half the story. Find where the taps actually land.
Seen and Unseen - medium - Every ping lands somewhere. Not every one gets read.
Did Anyone Actually Read It? - easy - A push isn't a win until a thumb taps it.
The Weekly Pulse - medium - Notifications by platform and day. When does the audience actually show up?
Nth Highest Salary Per Department - medium - Third place in every department.
The Upper Rungs - easy - The top rungs set the ceiling for everyone below.
The Vanishing Rows - easy - Some records disappear when the tables meet. Figure out why.
Oldest Alert per Service - hard - The oldest unresolved alert per service.
Oldest and Newest User Sessions - easy - The extremes of the user base.
The Scorched Earth Reviews - easy - Someone was unhappy. Find out how many times.
When They Opened - medium - Push after push goes out. Some months, people actually read them.
The Slow Lane - easy - Every route runs at its own pace. Find the ones lagging.
Where the Money Went - medium - Allocated on paper. Spent for real. Reconcile the two.
Overlapping User Sessions - medium - Two sessions, one user, same clock. Something overlaps.
Overloaded Infrastructure Nodes - medium - CPU above 90. Memory above 80. Red alert.
Pages Viewed by Session Duration - medium - Longer sessions, more pages? Check.
Pairwise Latency Maximum - medium - Every pair compared.
Peak Activity by Device - easy - Activity windows, device by device.
The Heaviest Hitters - easy - A handful of impressions earn more than the rest combined. Bring them to the top.
The Shape of a Day - medium - Traffic has a rhythm across the hours. Find where it runs busiest.
Peak Concurrent Batch Jobs - medium - Jobs pile up. Find the moment the scheduler sweats the most.
The Loudest Neighbor - hard - In every namespace, one pod does most of the eating.
All at Once - hard - How many tokens were alive at the same time?
Peak Hour Power Callers - medium - One hour. The phone lines exploded.
The Ides of March - medium - Every endpoint has one March it would rather forget.
Peak Metric Per Department - easy - Peak metrics for the quarterly deck.
Peak Non-Converting Month - easy - Everyone showed up. Nobody bought anything.
Peak Retargeting Revenue Month - medium - Retargeting revenue. The peak month.
Peak Satisfaction - easy - Which departments are winning on satisfaction?
Peak Spending Month - easy - One month, the bill was unforgettable.
Ghosts in the Scheduler - easy - It says running. It has been running.
Pipeline Completion Rate - medium - How far do users get through the flow?
Pipeline Duration vs Throughput - hard - Does throughput correlate with duration?
Pipeline Overhead by Environment - medium - Production overhead versus staging.
The Days That Line Up - medium - No key ties these tables but the calendar. Read it right.
Pipeline Run History - easy - The lineage trail.
Pipeline Throughput Ratio - easy - Compute current-to-initial value ratio per period.
The Shape of a User - medium - Every user leaves a trail of events. The report needs them lined up side by side.
Platform Check - easy - OS and device combos. Which sessions last longest?
Platform Speed - medium - Which devices keep users longest?
Platform Team Feature Flags - easy - The platform team owns a lot of flags.
Platform Team Mobile Flags - easy - Mobile flags under platform ownership.
Pod CPU to Memory Ratio - medium - CPU versus memory. Resource efficiency.
The Stable and the Restless - easy - Some pods never restart. That could mean anything.
Popular Categories - easy - Merchandising only cares about categories big enough to negotiate shelf space.
Power Users - medium - Engagement separates tourists from regulars.
Power Users by Session Activity - medium - More sessions. More time. The power users.
The Regulars - medium - Past a certain threshold, casual becomes committed.
Yesterday's Crown - hard - Every dawn inherits the spending of the day before.
Price Check - easy - Priced to sell or priced to sit?
Price Pairs - hard - Same shelf, wildly different stickers. Spot the pricing gaps.
Price Rank - medium - In every category, someone charges the most. Who's on top?
Priciest Item in Each Category - medium - The most expensive item per category.
Shipped to Prod - easy - Every environment keeps its own tally. Read the funnel.
After the Cutoff - easy - The calendar turned but prod kept moving. See which services never stopped shipping.
Product Name Letter Replace - easy - A quick text transform on product names.
Product Name Prefix - easy - Just the first three characters. That is all.
Everybody Wants a Bigger Screen - easy - The search bar never lies about what people actually want.
Product Ratings vs Sales - medium - Do higher ratings actually mean more revenue?
Product Revenue Ranking - easy - Rank them by revenue. See who leads.
Products Without Sales - easy - Listed but never sold.
Products With Strong Unit Price - medium - Budget-friendly and high-performing.
Product Transaction Counts - medium - Show how many transactions each product has, sorted by product ID.
Profitable Categories by Price - easy - The most profitable categories.
Profit Tiers - medium - High, moderate, or in the red. Every order gets a label.
Prolific Authors in Largest Service Teams - medium - Senior leads in the biggest teams.
The Price of a Tap - easy - The campaign fired thousands of pushes. Find what each open really cost.
Provider Cost Change H1 - easy - Cost swings in the first half of the year.
Provider Spend Variance Between Halves - medium - Two time windows. Did the cloud bill go up or down?
Purchase Log - easy - Names on receipts, not just IDs.
The Open Question - medium - Push sent. How many opened?
The Notification Lifecycle - medium - Sent, opened, ignored. What happened after the alert went out?
Push Opens by Platform and Campaign - medium - Opens by platform and campaign.
Q2 Search Volume - easy - Q2 search volume. The numbers.
The Weight of the Cloud - medium - Not every dollar counts the same. Close the quarter.
Q by Q - easy - Thirteen weeks. This is how the team spent them.
Quarterly Peak Cloud Costs - hard - Every quarter has a peak bill.
Quarters Apart - hard - Latency trending up or down? The quarters have the answer.
The Relentless Searchers - medium - Most users look once and leave. A few never stop looking.
Rapid Retry Detection - medium - Detect retried API calls within 5 minutes of failure.
Once and Only Once - hard - Repeated readings are noise. The value seen a single time is the signal.
Rate Limit Rules Per Endpoint - medium - Threshold rules, endpoint by endpoint.
Rating Tiers - medium - No gaps, no skips. Ratings stacked tight within each category.
Recent Price Drops - medium - The price just dropped. Who noticed?
Recurring Error Types - easy - The same errors, recurring.
Lines on the Map - medium - Every region keeps its own ledger. The totals set the order.
Regional Profits - easy - P&L by region. Before the board meeting.
Regional Sales Growth QoQ - hard - Quarter-over-quarter growth. Region by region.
Regional Status - easy - The full regional breakdown.
Regions by Alert Volume - medium - Some regions are quiet. Others never stop screaming.
Selling Where Nobody Lives - medium - Shipments land in regions our customer list has never heard of.
Regions With 5+ Nodes - easy - Regions with five or more nodes.
Where The Lights Stay On - medium - Every region promises reliability. See which ones keep it.
The Footprint - medium - Some regions carry more of the fleet than others. Show how it is spread.
Repeat Buyers Across Halves - medium - First half buyer. Second half buyer. Same person.
The Subscription Ghost - medium - Some charges come back to haunt the same card a month later.
Repeat Purchases Within a Week - medium - They bought again within seven days.
Repeat Purchase Window - medium - The retention squad is looking for repeat purchasers.
Repository Commit Ranking - medium - Lines added tell the story of a repo's ambition.
Repos with More Builds Than Commits - medium - More builds than commits. Something is off.
Resolved vs Unresolved Alerts - hard - Resolved versus open. By severity.
Response Buckets - medium - Fast, normal, or slow. Every API call gets a verdict.
Retargeting Campaign Impressions - easy - Retargeting impressions. All of them.
Retried Failed API Calls - medium - Spot users who retry API calls within 5 minutes of a failure.
Returning Buyers - medium - They came back and bought again.
Revenue by Product - easy - Which products carry the revenue line?
Two Names on the Ledger - easy - Two accounts. One ledger. Watch the spend stack up.
What the Shelf Never Sold - medium - Some products never moved a single unit. They still belong on the report.
Reviewer Performance Metrics - medium - Some reviewers are thorough. Others are fast.
Reviewers Per Repo Per Year - medium - Reviewers per repo, year by year.
Reviews Per Reviewer - easy - The workload split across reviewers.
Revoked Tokens by Scope - medium - Banned tokens, sorted by what they had access to.
Rolling Revenue Average - hard - Smooth out the revenue bumps. The trend matters more.
Spending Velocity - medium - Fraud hides in the pace, not the price. Watch each customer's last seven purchases roll forward.
Rows With Multiple Flag Conditions - medium - Rows caught by multiple flags.
In the Shadow of the Peak - medium - Every provider has a top-line cost. Find the one right behind it.
Running Node Pairs - easy - Two servers, same region, both alive.
Running Tab - medium - Every purchase adds to the total. Watch the tab grow.
The Accumulator - hard - A total that builds row by row. Structure the query to match.
Rush Hour API Latency - medium - Rush hour hits the API differently.
Same-Day Session and Transaction Correlation - hard - Same day session and purchase. Connected?
Honeymoon Phase - medium - Every signup class starts hot. Which ones spend the year they arrive?
Same First and Last Reply Target - medium - They started and ended the month messaging the same person.
Satisfaction by Platform - medium - Satisfaction scores, platform by platform.
Satisfaction Score by Region - easy - Satisfaction scores. Missing region data.
Search Algorithm Rating - hard - How good are the search results?
Search Endpoint Status Distribution - easy - Status codes on the health endpoint.
Searches by Users With Email - easy - One user's search behavior.
Search Success by User Tenure - hard - Compare search click-through rates between new and existing users.
Search Term Length vs Click Rates - hard - Longer queries, more clicks?
Search Terms Starting With G - easy - Queries starting with 'g'.
Second Highest Cloud Cost - medium - The second biggest bill on record.
Second Highest Latency by Method - medium - Almost the slowest. By method.
Second Highest Salary - easy - Silver medal. Almost the top, but not quite.
Second Highest Value - easy - Almost the top. Not quite.
Second Purchase - hard - The first buy is curiosity. The second is commitment.
Second to One - medium - Across every team, the pay figure that sits just shy of the summit.
Senior to Junior Ratio - medium - The ratio tells you a lot about the department.
Back From the Brink - hard - Roll it back, then nail the next one.
Servers Returning to Origin - medium - Servers that migrated back home.
Server With Most Errors - medium - One server stands out. Not in a good way.
Service Alert Frequency - easy - How often does each service trigger alerts?
Service Budget per Head - medium - Budget per head. Pipeline by pipeline.
Service Component Classification - medium - Classified by naming pattern.
Service Reliability Tiers - medium - Reliability tiers. Based on uptime.
Services at Median Uptime - medium - Exactly at the median. Not above, not below.
Service Scorecard - hard - Deploys vs. alerts. One row per service tells the whole story.
Services Hitting Cost Threshold - hard - The budget line is here. How many crossed it?
Services With Most Checks in 2025 - hard - Last year's most-checked services.
Services With Most Error Occurrences - easy - The noisiest services.
Services With Multi-Quarter Uptime - hard - Multi-quarter uptime streaks.
Service Uptime Minutes - medium - Status changed. How long was it actually up?
Service Uptime Turnaround - hard - It was down. Then it came back. Stronger.
Service User Growth Rate - easy - User growth, service by service.
Service With Most Critical Alerts - hard - One service keeps setting off the alarms.
Session Count Distribution - hard - How are sessions distributed among the newest users?
Session Duration by Account Status - medium - Average session duration broken down by user account status
Session-Fit Content - easy - Content that fits the session length.
Session Logins Dec 13 to 19 - easy - Logins during one specific window.
Session Overview - medium - Full engagement picture, even for the ones who never showed up.
Session Page View Distance - hard - Page view distance per session.
Session Pulse - easy - Engagement is slipping. Who is phoning it in?
Session Rank - medium - Longest sessions rise to the top. Within each user, a pecking order.
Sessions by Content Type - medium - Engagement, broken down by content format.
Sessions Per Device Type - easy - Sessions, device by device.
Shared Category Purchasers - medium - They bought different things from the same aisle.
Shared Channel Contacts - hard - User networks mapped through messages.
Shared Endpoints - medium - Shared credentials across endpoints.
Show all products in the 'Electronics' category - medium
Show all products NOT in categories 'Toys' or 'Games' - medium
This Year's Class - easy - The cohort is in. Time to count who made it through the door.
Signups by Age Bucket Since April - easy - Recent signups by age.
Who Comes Early - easy - Every year opens with a wave of new names. See how the first seven months compare.
The Conversion Story - medium - Signups are one thing. Paid purchases are another. Find the gap by source.
Silent Users - medium - Users who have never typed a query.
Single Service Owners - medium - One owner, one service. Nobody else.
Sirens and Smoke - easy - Stale alerts. Still ringing.
Slow Batch Jobs - easy - Promised by noon. Delivered at midnight.
Slow Failures - easy - SRE is hunting for the endpoints that fail slowly enough to burn timeouts.
The Address That Changed - hard - Addresses change. History must not be erased.
Slow Production Deploys - easy - Production deploys that took way too long.
Smooth Latency - medium - Noisy latency readings, smoothed into a trend you can trust.
The Compliance Order - easy - Token scopes need to be in the right sequence before the audit.
Spend and Rank - hard - Five thrones at the top of the spending leaderboard.
Spending by Account Status - medium - Segment user spending and activity by account status across the platform
Spending Range - hard - Between the smallest purchase and the biggest lies the story.
Spending Tiers - medium - High rollers, mid-spenders, and the frugal. Everyone gets a tier.
Split Metric Sums - medium - One column, two totals.
Status Report - easy - Where are orders getting stuck?
Stock Status - easy - Human-readable availability labels.
Storage Node Lookup - easy - The storage nodes hold the critical data.
Streak Status Changes - hard - Detect value changes across consecutive rows
The Holdouts - medium - Subscribed. But never upgraded.
Successful Build Duration by Repository - medium - CI throughput, repo by repo.
Successful Call Volume per Endpoint - medium - Not every ping is honest.
Green Lights on the Order Line - easy - How often did the orders API just... work?
Successful Pipeline Runs - easy - Which pipelines completed successfully?
Successful Production Deploys - easy - Successful production deploys with duration.
The Middle Ground - medium - Strip the outliers from both ends. What does the core actually add up to?
Super Reviewers - medium - The most prolific code reviewers.
Suspected Bot Sessions - easy - Five seconds or less. Probably a bot.
Symmetric Reply Network - medium - Who replies to whom? Both directions.
Tables With Many DQ Failures - medium - Some tables have never once passed QA.
Tables With Most DQ Failures - medium - The tables with the most failures.
Targeted Ad Campaigns - easy - High-value impressions. Targeted precisely.
Team Cost Allocation Comparison - hard - Individual spend versus team average.
Under the Line - medium - Twice the average is the ceiling. Find the teams comfortably beneath it.
Tenure Mentorship Match - medium - Pair by tenure. Longest with newest.
Time Served - hard - The tokens still in service each carry a history; measure how far it stretches, scope by scope.
The Ad Ledger - easy - Annual ad revenue. On the record.
The Biggest Fish - medium - In every aisle, one customer outspends the rest. Find them.
The Campaign Trail - easy - Impressions are vanity. Conversions are sanity.
The Cannibalization Report - hard - The new product launched. The old one suffered.
The Day-7 Retention Cohort - medium - Day one was promising. Day seven tells the truth.
The Dormant Accounts - easy - They are still paying. They stopped showing up.
Double Vision - easy - Before the records move, the ones wearing the same name twice have to surface.
The February Cohort - easy - One signup window. One cohort. Who joined the club?
The First Half - easy - New arrivals during one specific window.
The Heaviest Carts - medium - Inside every age group, a few customers carry the basket. Find them.
The Final Sale - medium - Every product has a last sale. When was it?
The Legacy Hunt - easy - Old data. Still matters.
The Lion's Share - medium - Every category claims its slice. Find out who really owns the table.
The Merge Counter - easy - How many builds came from merges?
Every Touch Counts - medium - A bid, a click, a search: each one is a vote. Total them honestly.
The Noise Floor - medium - Not every alert deserves a 3 a.m. page. Find the services where most of them claim they do.
The Ones That Move - medium - Every aisle has its champions. Surface the three that carry each one.
The Ones Who Finish - medium - Plenty of members press play. Far fewer reach the final rep. Find the formats that hold them.
The Ones Who Return - medium - One purchase is a trial. Two is a habit. Find how many members formed one.
The Phantom Readers - medium - They read everything. They bought nothing.
The Podium Finish - medium - Top two products per category.
The Provinces - easy - The home office isn't the whole story. Find the zones carrying the rest.
The Publishing Audit - easy - Published years ago. Still generating views?
The Quiet Alarms - medium - Low severity. High volume. Worth a look.
Two Sides of the Ledger - hard - Two cost tables, one region. Which way does the balance tip?
The Revenue Cliff - medium - Revenue was climbing. Then it wasn't. Spot the drop.
The Session Stitcher - hard - Page views without sessions are just noise.
The Slow Lane - medium - Peak API load. The slow endpoints.
The Token Census - easy - How many tokens are out there?
The Usual Suspects - hard - Same services, same checks, same problems.
The Weight of Everything Before - medium - Every purchase carries the ones that came before it. Trace the climb.
Third Highest Spender - medium - Bronze medal in spending.
Third Largest Batch Job - easy - Bronze medal in the batch job rankings.
Threads Excluding User - easy - Every thread they're not part of.
The Costliest Trio - medium - Three products, one price tag. Surface the priciest bundles.
Three Lowest Distinct Cloud Cost Amounts - easy - The three cheapest bills on record.
Three-Value Sum Combinations - medium - Pick three. See what they add up to.
The Transaction Breakdown - easy - Multiple time windows. One query. The business wants all of it at once.
Timeout Status Records - easy - Unknown status in the health records.
Timeout Warning Logs - easy - Timeout warnings. The postmortem trail.
Titles Ending With S - easy - Naming conventions. Specifically the plurals.
Keys That Never Die - medium - Some API keys have no expiry date at all. That should worry someone.
Tokens With Non-Read Scope Prefix - medium - Tokens that don't start with 'read'.
Top 100 Batch Jobs Total Output - easy - The hundred biggest jobs. Combined output.
Top 10 AB Test Variants - medium - The ten best-performing variants.
Top 10 Batch Jobs - easy - The ten biggest batch jobs.
Top 10 CPU-Heavy Nodes - medium - The ten hungriest nodes.
Top 10 Model Accuracies - easy - Top ten model performance.
Top 10 Rated Products - medium - The ten highest-rated items.
Top 10 Slowest Endpoints - easy - The ten endpoints nobody wants to call.
Top 2 Active Push Days - medium - Two days stood out from the rest. Which ones?
Top 2 Ad Campaigns by Spend - medium - Two campaigns. Most of the budget.
Top 2 Busiest API Slots - medium - Two time slots per week. The busiest.
Top 2 Callers per Endpoint - medium - Two top callers per endpoint.
Top 2 Cloud Services by Cost - medium - Two services eating most of the budget.
Top 2 Rate-Limited Clients - medium - Two clients are hitting the rate limit harder than anyone.
First Impressions - medium - The first three pages decide who stays.
Top 3 Monthly Costs per Team - hard - Three priciest months per team.
Top 3 Revenue Months - medium - The three best months on record.
Top 5 Slowest DNS Lookups - easy - Five DNS lookups that took too long.
Top Accuracy Model - medium - The single best-performing model.
Top Active API Tokens - medium - The five busiest tokens.
Top Active Senders per Channel - medium - Top three messages per channel by replies.
Top Ad Campaigns by Revenue - easy - Every campaign has a bottom line. Stack them up.
Top Alert Resolvers - medium - The engineers who resolve the most.
The Extremes - hard - Only the biggest and the smallest reach the executive review.
Top API Caller - medium - One user triggered more API calls than anyone.
Top API Token Scopes - easy - The highest-value token scopes.
Top Average By Region - easy - Region by region, who pulls the best average?
Top AWS Non-APAC Service Costs - medium - Outside APAC, AWS costs tell a different story.
Top Batch Job Under Priority 1 - medium - Priority one. Top performer.
Back Again - medium - Acquisition is expensive. These customers didn't need convincing twice.
Top Buyers of Premium Products - medium - Which users bought the most top-rated products
The Ones They Opened - medium - Every campaign fights for the tap. Find the ones beating the field.
Top Campaign by User Revenue - medium - Which campaign made each user spend the most?
Top Category by User Segment - medium - Each segment has a favorite category.
Top Chat Contributors - medium - The ten most active chat users.
Top Commit Authors by Repo - hard - Three authors per repo. The top committers.
Top Committers in 2025 - medium - In a sea of commits, only a few wear the crown.
Top Content by Lifetime Value - medium - Lifetime value. Measured in total watch time.
Top Content by Views - medium - Top five content items by views.
Top Content by Watch Time - medium - Some content holds attention. Others get skipped.
Top Content Flagger - medium - Flagged content. Who flagged the most?
Top Cost Categories - medium - Three categories eating the budget.
Top Cost Entry per Team - medium - The single biggest bill per team.
Top CPU Pods per Namespace - hard - The two most CPU-hungry pods in each namespace.
Top Deployed Model - easy - The best-performing model in production.
Top Device by Sessions - easy - One device type generates the most sessions.
Top Duration Content Items - easy - The content that held the number-one spot.
Top Earner Per Campaign - medium - The top-earning user per campaign.
Top Endpoint by Power Users - hard - Power users have a favorite endpoint.
The Loudest Failures - medium - Twelve months of errors. Which types showed up most?
Top Error-Service Pair - medium - Which error-service pair triggered the most resolved incidents
Top Five - easy - The five priciest items for the luxury section.
Top Flagged Campaign Resolutions - hard - Flagged the most. Resolved how?
Top Framework by Deployments - hard - The framework most often deployed.
Top Frameworks by Accuracy - medium - Top three frameworks by accuracy.
Top Identified Event Types - medium - The top users by events, but only the identifiable ones.
Top Lessons Each Month - medium - Rank items within time periods and keep top 3
Top Metric per Department - medium - Peak performer in every department.
Top Metric Values - easy - The five highest numbers. No duplicates.
Top Mobile OS by Session Duration - easy - Which mobile OS keeps users longest?
Competing Standards - hard - Every framework has a star model.
Top Pattern Matches - medium - A needle in a haystack, but how many haystacks?
Top Per Category - hard - Every category has a champion. Crown them all.
Top Percentile API Tokens - hard - The most suspicious tokens.
Top Percentile Spenders - medium - Top 1% of users by total spend via percentile bucketing.
Top Performing Models - easy - The models that actually perform.
Top Product Categories - medium - Top three categories by page views.
Top Product Categories by Sales - easy - The highest-grossing categories.
Top Product Category by Transactions - medium - Organic purchases, no marketing nudge. Which category wins?
Top Products by Quantity Sold - medium - The bestsellers. By volume.
Top Products per Category - medium - Five winners per category.
Top-Ranked Wines by Variety - easy - The best bottles. Ranked by variety.
Top Recent Sellers - easy - Fresh data, top sellers. The recent leaderboard.
Top Region by Order Volume - medium - The single busiest region.
Top Regions by Critical Alerts - medium - Which regions have the highest volume of critical alerts
Top Regions by Effective Uptime - medium - The most reliable regions.
Top Regions by High CPU Nodes - hard - Five regions with the hottest CPUs.
Top Repos by Commit Volume - medium - The most active repos in the org. No ties left behind.
Top Repos by Successful Builds - medium - Green builds. Which repos lead?
Top Revenue Products H1 - medium - First half of the year. Which products led the revenue race?
Top Selling Items - easy - Revenue crowns the winners. Who sold the most?
Top Services by Regional Cost - medium - Top spenders in one region.
Top Services by Uptime - medium - Uptime is a competition. Which services never blink?
The Heavy Hitters - medium - Within each cloud, two services rise above the rest.
Top Shelf - easy - Buyers need to know ceiling prices before negotiating with vendors.
Top Spender - medium - When your spending exceeds the priciest item on the shelf.
The Spender Leaderboard - easy - Spending speaks. The leaderboard does the listening.
Endless Scroll - medium - Some visitors never close the tab. Find the five who go deepest.
Top Users by Recent Spend - medium - Big spenders in the last 30 days.
Top Users by Session Time - medium - They spent the most time here.
Total Compute Cloud Cost - easy - Total compute spend. The number.
Total Cost by Category - easy - Total spend per category.
Total Engineering Cost Allocation - easy - Engineering's total allocated budget.
Total Hours Between Consecutive Events - hard - Hours between state changes.
Total Rows by Pipeline Status - easy - Row counts alongside pipeline aggregates.
Total User Spend - easy - Each customer's total. Summarized.
Only Here - hard - Exclusive to one source. Missing from the other.
Transaction Overview - easy - The executive snapshot. Users, products, revenue.
Deep Pockets - medium - One month, every customer, every dollar accounted for.
Transaction Share of User Spend - medium - Each transaction's share of the whole.
Transaction Source Features - easy - One pipeline reviewed them. What did it see?
The Named Transaction - easy - Transaction IDs are useless without context. Bring in the product names.
Transaction Timeline - medium - First purchase to last. The full spending arc.
Trend Spotter - medium - What did they spend last time? Context changes everything.
Trim Endpoints Right - easy - Trailing whitespace. Clean it up.
Trim Search Terms Left - easy - Leading whitespace. Clean it up.
Read the Manual - easy - Some titles promise to walk you through it. Count the ones that say so out loud.
Unclicked Searches by Campaign - medium - Searched but never clicked.
Unique Hostnames per Region - medium - How many distinct machines live in each region?
Unique Hosts by Node Type - easy - How many unique hosts per node type?
Unique Reporters per Content - medium - How many people flagged each item?
Unique Searchers - easy - How many users actually searched?
Who's Looking - easy - Every search is a question someone needed answered. Count the people asking.
Unique Stream Topics - easy - A clean inventory of streaming topics.
Unique Visitors - easy - Which months actually had an audience?
Unmatched Categories - easy - Categories with nothing on the shelf. Empty aisles.
Buyers Who Never Browsed - easy - They bought without ever loading a page.
Unmatched Deploy Services - medium - Two registries. They do not agree.
Unreviewed Models - easy - Models that have never been evaluated.
Unsold Product Categories - medium - Dead inventory inflating storage costs.
Unused Read Tokens - easy - Active tokens that nobody uses.
Age of Discovery - hard - Every generation searches differently. See who finds what they came for.
Where in the World Are Our Customers? - medium - One country dominates the logo wall. Or does it?
Use APPROX_DISTINCT to estimate the number of unique users who have made transactions - medium
US-East KV Store Entries - easy - KV store inventory. us-east-1.
User 360 - hard - One row per user. Everything they did, or didn't do.
User Age Ranking - easy - Age brackets, stacked from top to bottom.
User Campaign Overlap Percentage - hard - How much ad overlap between users?
Six Degrees - hard - Every reply ties two names together. Find whose web reaches the furthest.
User Devices - medium - Desktop, mobile, tablet. What does each user actually use?
User Engagement Summary - medium - Sessions plus searches. The full engagement picture.
Where the Minutes Go - easy - Time spent, and everything they touched.
Behavioral Range - easy - Power users don't just visit more. They do more things.
User Roster - easy - Which account states are bleeding users?
User Session Roster - easy - Every user paired with their sessions, even users who never logged in
User Sessions on Specific Days - easy - One user. Specific days. What happened?
Users Outperforming Control - medium - Treatment beat control. For these users.
User Spend Audit - medium - One user. One category. Total spend.
Tiers of Want - hard - In each category, some carts weigh more than others. Sort the shoppers by what they spend.
Users Per Device Type - easy - Users per device. The split.
Users Who Churned in February - hard - Gone in February.
Users Who Clicked Ads - easy - Ad clickers and their account details.
Users With Admin Tokens - medium - Admin tokens. Who holds them?
Users With and Without Ad Clicks - hard - Clicked an ad versus never clicked. The split.
Users With API Errors - medium - Count unique users who have triggered an API error response
Users Without Purchases - medium - How many registered users have never made a single purchase
Users Without Sessions - medium - Account created. Never logged in.
Users With Purchase Events - easy - At least one purchase. That changes everything.
User With Most Transactions - medium - The most active buyer.
Verify Commit ID Uniqueness - easy - Duplicate commit IDs. Are there any?
View Count Per Page - easy - Every page has visitors. Some just have more.
Point of Entry - hard - Everyone starts by looking. Count who came back to buy.
Views by Content Type - medium - Count content views broken down by content type
Views by Specific Users - easy - Retrieve all content views for a set of flagged user accounts
Weekend Warriors - easy - Weekdays vs. weekends. When does the action really happen?
Weekly Build Status Report - hard - Every CI run, bucketed by week.
Bookends of the Week - hard - Every week has two edges. Weigh what lands on each.
Weekly Transaction Volume - easy - Weekly volume. The pulse.
Weighted Variant Selection - hard - Select a row using cumulative weight probabilities.
Welcome Wagon - easy - How many signed up this year?
Whale Watch - easy - The accounts driving the top line.
Where the Data Breaks - medium - Every dataset has a weak point. Surface the ones the checks already caught.
Where the Money Pools - medium - Every region has one line item that dwarfs the rest. Find it.
Word Count Per Message - medium - How wordy are the messages?
Workers Earning Above Department Average - medium - Earning above the department average.
Worst Table Per Year by DQ Failures - hard - Every year has a worst table.
Against the Clock - medium - Build times by repo, year by year.
Yearly Output - easy - Publishing velocity for the board deck.
Year-over-Year Content Launches - medium - Launch velocity, year over year.
YoY Signup Growth Rate - hard - This year versus last year. Growing or shrinking?
Stumbling Out of the Gate - medium - Some model versions never recover from a bad opening run.
Zero-Retry Job Ratio by Priority - hard - No retries needed. First try success rate.

Pipeline Architecture (144)

45 Minutes Turned Into 3.5 Hours - medium - Spark jobs are running. Just not fast enough.
600 Million Events a Day - hard - 600 million events a day. Two years of retention.
A Clean Number for Every Merchant - hard - Raw payment logs in. Clean merchant summaries out.
A Million Cars Phoning Home - hard - Every vehicle is a sensor. Deploy the pipeline to catch it all.
A Million Moving Dots - medium
Analysts Are Slowing the Store Down - medium - Orders placed. Data warehouse hungry.
A New Column on a Billion Rows - hard - Add and backfill a new column to a billion-row production table with zero downtime.
A Shared Drive Full of Contracts - medium - Buried in PDFs. The data is in there somewhere.
A Stream All Day and a File at Midnight - hard - Real-time and batch. Same pipeline. No compromises.
Badging Items That Already Sold Out - hard - Same-day delivery. The features have to be faster.
Basel, CCAR, and Monday Morning - medium - The regulator does not accept 'eventually consistent.'
Before the Batch Is Lost - hard
Bikes Before Rush Hour - hard - Bikes in, bikes out. The city needs to predict demand.
Credit for Every Touch - medium - They saw the ad, clicked the email, then bought. Who gets credit?
Disappearing Ink - easy
Everything Lands, Then It Ships - medium
Doubling Every Six Months - hard - Tuesdays are quiet. Black Friday is not.
Eight-Hour-Old Positions - hard - Positions shift by the second. The math cannot lag.
Eight Teams, Eight Latencies - medium - Millions of gamers. The architecture decision changes everything.
End of Day Is Too Late - medium - Every swipe tells a story.
Equities, ETFs, and the SEC - hard - Fractional shares, multi-currency, point-in-time. All of it.
Event System for Multiple Consumers - hard - One event, many hungry consumers.
Every Dataset Needs a Paper Trail - hard - The FDA has opinions about your data pipeline.
Every Deal Is a Financial Transaction - hard - Real money on the table. Reconstruct every hand.
Every Device, Every Impression - hard - Every ad seen. Every second watched. Real-time.
Every Device Has Its Own Dialect - medium - Three sources. Three formats. Same workout.
Every Firm Formats It Differently - medium - The regulator changed the format. Again. Handle it.
Every Format Imaginable - hard - PDFs, HL7, JSON. All of it lands in the same lake.
Everyone Wants the Same Data, Differently - hard - How you store it decides how fast you can read it.
Every Region Exports Its Own Way - medium - Sales data, BigQuery, Dataflow. Make it all sing.
Every Scan, Every Parcel, Every Pin Code - medium - Out for delivery. Delivered. Except the events arrived backwards.
Every Version of You - medium
Fifty Thousand Retailers - medium - Retail data at CPG scale. Every SKU, every store.
Five Times the Traffic, Five Times the Bill - hard - Scale up when needed. Do not bankrupt the team.
Five Years of Cron Jobs - hard - Half the jobs run on cron. Half run on events. All of it has to move.
Flying Blind Until Midnight - hard - Intraday risk, full lineage. The regulator is watching.
Four Teams, One Topic, No Agreement - hard - Everybody is writing to it. Nobody documented it. Now production is fragile.
Fresh and Forever - medium
Greenfield Build for Six Sources - hard - Infrastructure as code. Meaning as a service.
Half a Million Rental Cars - medium - Every vehicle is reporting. Every rental matters.
The Identity Problem - hard - Old systems. New demands. The same customer appears under three different names.
Listens From Everywhere, Counted Once - hard - Phones, tablets, laptops. And some of them report late.
Live Viewers, Live Billing - hard - The stream is live. The data cannot wait.
Mark to Market - medium
Near-Real-Time Trending Dishes Dashboard - hard - The dish rankings update faster than the kitchen.
Nested Docs, Flat Reports - medium - Two databases. One direction. No data left behind.
Nightly Exports Are Too Slow - medium - Healthcare claims change constantly. The warehouse cannot fall behind.
4,500 Stores Before Sunrise - medium - The shelves open at 7. The data better be there.
Not Every Team Can See Every Row - hard - Everyone can see the bucket. Not everyone should.
One Bill Across Three Clouds - medium - AWS, Azure, GCP. Three bills. One truth.
One Earthquake, Ten Thousand Tweets - hard - The firehose is on. Separate signal from noise.
Out of the Data Center - medium - The on-prem servers are not getting any younger.
The Speed Layer - medium - Dashboards can't wait for raw logs. Something has to happen upstream.
Prove the Number Is Right - hard - Bad data in fintech is not just messy. It is expensive.
Real Data, Fake Patients - hard - Dev needs production data. HIPAA says absolutely not.
The Register Never Sleeps - medium - Every swipe lands in the warehouse. The table has to stay current without breaking.
Recommendations Now, Royalties Later - medium - The catalog updated. Did anyone notice?
Replicate It Without Breaking It - hard - The source changed. The lake needs to know immediately.
Risk Models on Week-Old Data - medium - Loan approved. Loan denied. Every decision is an event.
SaaS API Connector with Incremental Sync - medium - The API has rate limits. You have deadlines.
Same-Day Sales, Every Store - medium - The cash register data needs to be queryable by morning.
The Living Table - medium - Data lands continuously. History must survive every update.
Score It Before It Clears - hard - The fraudsters move fast. Your pipeline has to move faster.
Seconds and Months - medium
Seconds to Trend - medium
Ship Before Fraud Finishes Checking - hard - The claim looks clean. The fraud model disagrees.
Six Hours to Miss a Deadline - medium - The rebuild works. It just doesn't finish in time.
Six Hours to Refresh Every Number - medium - Ratings change. The incremental model has to keep pace.
Six Million Rows Before the Market Opens - medium - One massive CSV. Millions of timestamps.
Six Sources, One Platform - medium - ADF orchestrates. Unity Catalog governs. Nothing leaks.
Sixty Minutes, Every Hour - medium - Every hour, on the hour. No excuses.
Someone Else's Server - hard
Stores and the Site, Together - hard - The registers never stop ringing.
Store, Site, and Distributor - medium - Sales data is piling up. Someone has to make sense of it.
The Acquisition Still Taking Bookings - hard - Two systems, two schemas. One truth.
The Agency That Changes the Columns - medium - The schema changed overnight. Again.
The Analysts Cannot Touch Production - medium - Production is the source. Analytics needs its own copy.
The Analyst Who Saw the Salary Data - hard - Two incidents. One shared lake. The access model was never designed, just assumed.
The API Drip Feed - medium - The API gives you 100 records at a time. You need millions.
The Bad Row That Broke the Dashboard - medium - Bad records cannot reach the warehouse.
The Binding and the Claim - medium - Policies are instant. Claims take their time.
The Booking That Came Three Ways - hard - PMS, OTA, and website all think they took the reservation first.
The Boutique That Sold in Six Currencies - hard - Every sale is real. The rate it was converted at depends on who is asking.
The Bucket Full of Resumes - medium - A thousand resumes. Structured data inside each one.
The Carrier Moving to Azure - medium - Claims arrive messy. The medallion cleans them up.
The Claim That Picks Its Own Lane - medium - Three entry points. Different workflows. All must route correctly.
The Clicks We Throw Away - hard - Every tap, swipe, and scroll. At scale.
The Clock That Runs Two Ways - hard - Nightly batch and live events. One dashboard.
The Consent Stitcher - medium - Consent was given. Or was it? Stitch the records together.
The Dashboard and the Attribution Model - hard - Streaming and batch. One pipeline to rule them.
The Decision Before the Door Closes - hard - The window to stop it is smaller than you think.
The Distributor Filing Problem - medium - Hundreds of suppliers. One warehouse. One deadline.
The Early Warning - medium
The Event Pile - hard - 600 million clicks a day. The budget is not infinite.
The Fare Aggregator - medium - Airfares shift every minute. Catch the best ones.
The Firehose and the Ledger - hard
The Fleet That Never Stops - hard - Every truck is talking. Not everyone can hear them yet.
The Leaderboard That Costs $25K a Month - hard - Product wants it live. Engineering has a price tag.
The Ledger and the Live Wire - hard
The Meal Kit That Knows You - medium - What they ordered says a lot about what they want next.
The Metric That Moved - medium
The Migration That Cannot Break Morning - hard - It all works today. Moving it without losing a single report is the hard part.
The Models Going Stale - hard - The model is only as good as what you feed it.
The Morning File - medium
The Next Track - medium
The Panel and the Set-Top Boxes - hard - Set-top boxes tell you who watched. Projection tells you how many.
The Patients We Cannot Move - hard - Patient data stays local. Insights have to be global.
The Points Arrive Two Days Late - medium - The bank data shows up late. The rewards were already sent.
The Provider That Sometimes Sleeps - medium - The models run at dawn. The data has to be there first.
The Query That Used to Be Fast - medium - Queries used to be fast. Something changed.
The Queue That Wouldn't Stop Growing - medium - 500,000 messages behind and the number keeps climbing.
The Revenue That Was Wrong for Two Weeks - medium - Nobody caught it until the CFO asked a question. Design the system that catches it first.
The Sale That Needs to Land Now - medium - Three channels feeding one view. Not all of them speak the same language.
The Same Stream Twice - hard
The Signals That Power Recommendations - medium - Fresh signals, many teams, one pipeline.
The Thirty-Second Rule - medium
Counted Once, Remembered Forever - hard
The User Who Asked to Be Forgotten - hard - Users want their data erased. Completely.
The Vendor Who Never Warns You - medium - Every month, something is different. The dashboards have no idea.
The What-If Machine - hard - A million slots. A thousand campaigns. Every combination matters.
The Whiteboard Exercise - medium - Marker in hand. Draw the whole thing.
Thirty Cities, One Forecast - hard - Five cities. Five data formats. One prediction.
Thirty Countries, One Solvency Number - hard - Premiums collected globally. Losses happen locally.
Thirty Million Unique Jobs a Year - hard - One press run, many orders. Group them right.
Thousands of Practices, One Dataset - hard - Patient records in, operational insights out.
Three Providers, One Workout - hard - The same ride, reported three times.
Three Regions, One Finance Team - hard - Payments from everywhere. One consistent report.
Three Regions, One Report - hard - Three regions, billions of payments, one merchant summary by 6 AM.
Towers and Phones, Same Story - hard - Tower signals meet app events. Somewhere in between is the truth.
Traders, Risk, and the Regulators - medium - Markets move in milliseconds. The pipeline has to keep up.
Two Hundred Million Redirects - medium - Billions of clicks. One tiny code. Two very different clocks.
Two Million Boxes by Monday Morning - hard - Shipped, maybe. Delivered, debatable.
Two Sources of Truth - medium
Two Systems, One Room Count - hard - Two booking systems. Rooms do not duplicate themselves.
Two Ways to Catch a Change - medium - Two ways to watch the database. Each has a cost.
Two Years of Every Click - hard - Every click, every aisle, every day for two years.
Two Years of Clicks, Cheap - hard - Two years of clicks. Every query has to be affordable.
What Everyone Is Watching - hard - Someone is watching. Capture everything.
What Should We Recommend Tonight - hard - They ordered pad thai twice. That means something.
Where Is Every Truck, Right Now - medium - Trucks are moving. Every ping counts.
Where the Crowd Goes - medium
Which Promotion Is Actually Working - hard - Was the promotion worth it? The data knows.
Who Is Churning and Why - medium - Subscribers churn. The pipeline cannot.
Who Saw the Ad Twice - hard - TV and digital. Same viewer, two measurement worlds.

Data Modeling (63)

Split Decision - medium - One user, one experiment, one variant. No exceptions.
Where They Used to Live - medium - They moved. The data stayed behind.
The Double Count - medium - One flight carries hundreds of seats; one ticket spans many flights. Model them so neither gets counted twice.
A Number for the Seller - easy - They want a total. Give them the right schema first.
B2B Invoicing Data Model - easy - Invoices go out, partial payments trickle in, and some customers are three months overdue.
The Anonymous Majority - medium - Millions of clicks, mostly anonymous.
Cloud File Storage Metadata Schema - hard - A file is also a folder. A folder is also a file.
Content Engagement Data Model - hard - Post published. Now measure everything that happens next.
Content Search and Discovery Schema - hard - Searchable from every angle. Design it so nothing gets lost.
Customer Address History - easy - People move. Sometimes twice in a month. How do you remember where everyone was, and when?
E-Commerce Supply Chain Tracking - hard - A package splits, reroutes, and (maybe) arrives.
Signal and Silence - medium - They opened the assignment. Did they actually read it?
Employee Application Time Tracking - medium - Every minute tracked. Every app accounted for.
Employee Transfer Tracking System - medium - People switch teams. HR loses track.
Event Ticketing System Data Model - easy - JSON in. Reporting warehouse out. Design both ends.
Financial Trading Warehouse - hard - Every trade, every tick, every fraction of a share. The regulators want receipts.
Personal Best - easy - Reps, sets, streaks, and personal bests. Gym rats love their stats.
The No-Show - easy - Every reserved seat ends one of five ways. Build the model that can tell them apart.
Food Truck Operations Data Model - medium - Mobile vendor, fixed menu, unpredictable locations.
Deal Flow - medium - Sellers want buyers. Buyers want deals.
Insurance Claims Lifecycle - hard - A claim gets filed. Then it gets complicated. Then it gets reassigned. Then it loops back.
Livestream Analytics Schema - medium - Someone goes live, thousands tune in, chat explodes, and virtual gifts start flying.
Approval and After - medium - Approved, declined, or pending. Design the tables that say so.
The Balance Always Reconciles - easy - Money out, payments back. The balance has to be exact.
The Vital Few - medium - Two terabytes a day, and the lines that matter are a rounding error in the noise.
The Shape of a Run - medium - Two log lines bracket every process. Pair them and the fleet's rhythm appears.
Marketplace Sales Warehouse - hard - No schema given. The interviewer is watching.
Metric Definition Reverse Engineering - hard - Five numbers on a dashboard. Your job: figure out where they come from.
Movie Streaming Analytics Schema - medium - They pressed play. What happened next is the whole question.
Multiplayer Game Match History - medium - Millions of matches. The leaderboard refreshes in fifteen minutes.
Online Marketplace - Seller Payouts - hard - The buyer paid one number. The seller got a different one.
The Retail Blueprint - medium - One business. A thousand transactions. Only one layout survives the analytics layer.
The Last Mile - medium - Order placed. Now track it to the door.
POS Sales Data Warehouse - medium - Every beep at the register. Coupons, returns, all of it.
Property Booking Platform - hard - Five-star listing. Three-star reality.
Retailer Data Warehouse Design - medium - Queries are crawling. The analysts are not happy.
Ride-Sharing Platform Schema - medium - Riders, drivers, and fares. Everyone takes a cut.
The Sales Architecture - medium - Numbers are easy. Making them queryable at scale is the real job.
The Customer Who Changed - hard - She moved. She upgraded. She became someone new. The record has to keep up.
The Endless Thread - medium - Follows, likes, replies to replies. It never stops.
Two Wallets - medium - Two user types. Multiple payment methods. One messy billing table.
When the Music Stops - medium - Subscribers are leaving. The data knows why.
The Heat of the Map - hard
Telecom Network Connectivity Warehouse - hard - One device goes down. The ripple keeps going.
The Celebrity Problem - medium - One post. A million notifications. Something has to give.
The Churner Who Came Back - hard - They cancelled. They came back. The report has to tell both stories correctly.
The Gaps Between Clicks - hard
The JSON Files That Became a Data Mart - medium - Three semi-structured inputs. One queryable warehouse.
The League With Too Many Loyalties - hard - A player can belong to many teams. The schema must agree.
The Other Seat - hard
The Person They Were Then - easy
The Plan That Changed Twice This Month - medium - Subscribers come, go, downgrade, and share. The schema has to keep up.
The Retail Tables That Need a New Home - medium - A working system. Now redesign it so the analysts can actually use it.
The Schema That Could Not Answer Back - hard - Forty columns in. Zero useful answers out.
The Slow Yes - hard
The Table That Lies - medium - Every query comes out wrong. The data is all there.
The Talent Funnel - medium - Thousands applied. One accepted. Where did the rest go?
The Territory That Keeps Moving - hard - Reps get reassigned. The receipts have to survive.
The Transfer Request - medium - Apply, wait, get approved or denied. Track all of it.
Three-Sided Marketplace Delivery Schema - hard - One order. Two deliveries. Revenue counted twice. Where is the bug in your schema?
Toll Road Sensor Analytics - easy - Cars enter, cars exit. Except when they don't.
Trending Dishes Dashboard - medium - What's everyone eating? The answer changes hourly.
Who Comes Back - medium

Python (412)

Activity Time Ledger - easy - Matching activities. One runtime.
Closing Time - easy - Every bracket you open is a promise. Check that the parser keeps all of them.
Birds of a Feather - medium - Every record finds its kin; keep them in the order they arrived.
Batch Records - medium - Too many at once. Break them into groups.
Batch With Metadata - easy - The list gets chopped.
Between the Clicks - medium - Clicks arrive scrambled. Find where one visit ends and the next begins.
Caesar Shift Check - easy - The key turns. Does it open?
Carry the One - medium - In grade-school subtraction you scribble a mark each time you borrow. Recover those marks.
Letters in the Noise - easy - Case and punctuation are distractions. Find what each letter really weighs.
Char Profile - medium - Every character in the string tells a story.
The Fallback Layer - easy - When the live values come back empty, something has to stand in.
Column Max - easy - One value rules the column.
Column Range - easy - From minimum to maximum. What is the spread?
All Told - easy - Every shift leaves a number behind. Total the fleet.
Common Prefix - hard - They all start the same way. How far?
Cumulative Sum - medium - The total grows with every row.
The Gaps Between - hard - The data is not as clean as it looks.
All the Way Down - medium - However deep it nests, every leaf belongs on one line.
The Path Inward - medium - Every setting hides a few levels down. Follow the route, or come back empty.
Full Circle - medium - Follow the chain long enough and it might loop back.
Detect Outliers - medium - Most values are normal. Some are suspicious.
Corner to Corner - medium - Not every value sits in a row or column.
Dice Roll Scoring - medium - The pattern rewards the patient.
Dictionary Key Intersection - medium - Two dictionaries. What do they share?
The Carousel - medium - Every value takes its turn; the wheel keeps spinning.
Dominant Element - easy - Majority element. Appears more than half the time.
Even Filter - easy - Only the even ones survive.
Everything Beneath - medium - Every account carries the weight of all it contains.
Execution Timer Wrapper - medium - Function wrapped with a timer. Duration captured on exit.
Explode List - easy - One row holds many values. Unpack it.
Extract Domain - easy - The domain is buried in the string.
Extract Leaf Values - medium - The tree has leaves. Pluck them.
Find Indices - medium - It is in there somewhere. Where exactly?
Find Mode - medium - One value appears more than the rest.
Who Came First - easy - The feed repeats itself. Keep each member only the first time it speaks.
All the Way Down - easy - Sections nested inside sections. One stream, in order.
Flatten the Nest - easy - Mixed nesting. One flat list out.
Full Outer Zip - medium - Two sides. No value left behind.
Greeting Formatter Class - easy - First impressions are formatted carefully.
Group Average - hard - Same group, different values. What is typical?
Group By - medium - Same key, different rows. Bring them together.
The Spaces Between - medium - Every voided trip leaves a hole in the sequence. Find the one that matters.
Lag Column - medium - What came before this row?
No One Left Behind - medium - Every record stays; fill the gaps where a match exists.
The Loudest Voice - medium - One event type is drowning out the rest. Find it.
Max Length Token - medium - The longest token wins.
Merge Counters - medium - Two tallies. Combine them.
The Overlap - hard - Overlapping windows are one outage. Collapse them into the truth.
Back to Back - medium - Windows stacked on windows. Find the real spans.
What the Day Left Open - medium - Every fill moves a position. Reconstruct where the book settled by the close.
Normalize Name - easy - Names are messy. Standardize them.
No Shortcuts - easy - The peak value. Built-ins off the table.
Null Counter - easy - How many holes in the data?
Right of Way - medium - Every packet asks the same question of the firewall. Answer it the way the table intends.
Ordered Character Check - easy - Check if all As appear before all Bs.
Reads The Same Both Ways - medium - Somewhere in the noise, a stretch that mirrors itself. Find the longest one.
Parse Log Line - medium - One line. A dozen fields hidden inside.
Who Gets In - medium - When the roster changes, does access follow?
The Wide View - hard - Long format is easy. Wide format is useful.
Portfolio Profit Calculator - medium - Portfolio gain from purchase history and current prices.
Precision and Recall - medium - Precision and recall. Both matter.
Prefix Based Word Replacement - medium - Every word trimmed to its root.
Progress Milestones - easy - Progress at every 10% increment. Keep the receipts.
Quality Gate - easy - Not everything passes inspection.
Quantile Calculator - easy - Mark the boundary value at a given point.
Points of Order - medium - Every page makes its case for the top. Settle it, and settle the ties.
Read Both Ways - easy - Placeholders hide in plain sight. The symmetric ones give themselves away.
Every Line on the Receipt - medium - Nested deep inside the receipt. Pull every item out.
Record Filter - easy - Some records belong. Others do not.
Rename Keys - medium - Old names out. New names in.
Reverse Field - easy - Flip it. See what happens.
Between the Pings - medium - The fleet never stops talking. Find where each vehicle paused.
Full Circle - medium - Load has to keep moving. Pass it down the line.
Row Aggregates - medium - Each row holds its own summary.
Run Length Encoding - easy - AAABBB becomes 3A3B. Compress it.
Running Distinct Count - medium - New values keep appearing. Track the count.
Sanitize Field - easy - Dirty input. Clean output.
Schema Checker - easy - The schema says one thing. The data says another.
Sequential Word Pairs - easy - Everything has a neighbor.
Shortest Unique Metric Tag - medium - One token per metric. Make it unambiguous.
Single Element Among Pairs - easy - One element has no partner.
Sort Descending - easy - Biggest first. No exceptions.
Stock Range Finder - medium - Prices move. One stretch had the widest gap.
Against the Current - hard - Too big to load. Read what you can.
Subarray Signal - medium - One stretch carries the strongest signal.
The Account Manager - easy - Deposits, withdrawals, and the risk of going negative.
The Additive Chain - easy - Each value is the sum of the two before it - no calls to itself allowed.
The Address Surgeon - easy - One string hides a street, a city, a state, and a zip.
The Alphabet Score - easy - Every letter has a secret numeric value - what's your total?
The Alphabet Sorter - easy - Filing cabinet logic: everything goes in its proper drawer.
The Spike - hard - Spot the outliers before they page someone.
The Balanced Inspector - medium - Every branch should carry the same weight.
The Balanced Sum - easy - Some numbers have a rare quality that mathematicians revere.
The Bipartite Test - medium - Can this crowd be split into two perfectly separated groups?
The Bit Counter - easy - How many lights are on in the binary representation?
The Bit Ladder - easy - Count the ones all the way up.
The Bit Reverser - medium - Sometimes the answer is literally backwards.
The Bitwise Judge - easy - No division, no modulo - just a single bit tells you everything.
The Blind Multiplier - medium - Compute the result of everything around you - without seeing yourself.
The Bonus Round - medium - Consecutive matching dice rolls trigger a special scoring rule.
The Bouncer - easy - Every door has a guest list.
Open and Shut - easy - Every opener is a promise. The order you close them in decides whether it holds.
The Bronze Medalist - easy - Not first, not last - somewhere in the middle of the podium.
The Budget Allocator - medium - Split the money. Some wore two hats.
The Bug Spotter - easy - It compiles. The answer is still wrong.
The Build Order - medium - Some tasks must wait for others to finish first.
The Calendar Sort - easy - Time has its own opinion about order.
The Carousel - easy - Keep moving, same ride.
Best in Class - medium - Every category keeps its leaders. The rest fall away.
What Stays Warm - medium - Memory is small and the stream never stops. Keep only what was just asked for, in the order it was asked.
The Chain Transform - medium - One small step at a time can cover a great distance.
What the Night Changed - hard - Two photographs of the same table, a day apart. Account for everything that moved.
The Change Tracker - medium - Before and after snapshots. The delta is in there.
The Character Clans - medium - Words sharing the same letters belong to the same clan.
The Squeeze - easy - Long stretches of sameness collapse into almost nothing.
The Character Map - easy - Character-level frequency. As a dictionary.
The Chunked Reader - medium - Too big for memory. Read in pieces.
The Cipher Wheel - easy - Every letter has an alias - you just need the right codebook.
Hands Apart - easy - Two hands. One gap. One number.
The Clock Examiner - medium - Two hands on a clock: how wide is the gap?
The Code Expander - easy - Compressed messages need a decoder to come alive.
The Coin Vault - medium - Exact change only - and you want to use as few coins as possible.
The Column Shuffle - medium - Rows in, columns out. Number them.
The Column Transformer - easy - Each column gets its function.
The Roll Call - easy - Every value is waiting for its name.
The Complement Hunt - easy - Every number is looking for its other half.
The Config Blender - easy - Config collision. The surviving values after a merge.
The Unbroken Line - medium - Numbers that flow without interruption.
No Days Off - medium - Show up every day. Miss one and the count starts over.
The Counting Machine - medium - It knows where it stopped last time.
The Crowd Favorite Eatery - easy - One restaurant clearly won the most hearts.
The Crowd Pleaser - easy - One value shows up more than all others combined.
The Crowd Splitter - easy - The middle holds even with a dominant outlier.
The Custom Iterator - medium - Some sequences follow their own rules.
Full Circle - medium - Follow the chain long enough and you might end up where you started.
Downstream - hard - Nothing runs until what it needs has run.
The Date Sorter - medium - Jumbled calendar. Sort it first.
The Decomposer - easy - Every composite thing can be broken down to its simplest parts.
The Deep Config - medium - Every setting has a path. Trace it down to the value.
The Deep Dictionary - easy - One key goes further than the rest.
The Deep Dive - easy - A specific position in the unsorted pile.
The Deep Selector - easy - Tell it what you want. It knows where to look.
The Deep Unpacker - easy - Boxes inside boxes. Eventually you reach the bottom.
The Dependency Resolver - medium - Everything depends on everything.
The Depth of Field - easy - Some containers hold containers that hold containers.
The Diagonal Accountant - easy - Two diagonals cross in the center of every square.
The Dict Comparator - medium - Two dictionaries. Subtle differences.
The Mirror Index - easy - Every value remembers who pointed to it.
The Disputed Fare - medium - One charge, two legs. Finance needs to know which two.
The Dominant Signal - easy - Hottest items in the transaction log. Ties included.
The Double-Ended Gateway - medium - Some queues let you skip the line from both ends.
The Duplicate Spotter - easy - Some values appear more than once - report only those.
The Dynamic Container - hard - Grow your own storage before the standard library does it for you.
The Elevator Trace - medium - Nested floors. One path through.
The Email Ranker - medium - Some inboxes see more action.
The Encoded Signal - medium - Letters folded into digits, counts hidden in the punctuation.
The Even Checkpoint - easy - Is this number in the even club? Prove it the fast way.
The Firehose - medium - A stream arrives out of order. Roll it up, one time window at a time.
The Event Broadcaster - medium - Subscribers show up, listen, and sometimes leave.
The Event Bucketer - easy - Logs slotted into buckets.
When Hours Collide - medium - Two reservations, one slot. Find every clash.
The Event Window - medium - A five-minute window is all that matters.
The Eviction Policy - medium - Fixed capacity. The key left idle longest is the one that goes.
The Exception Handler - medium - Good code handles failure as gracefully as success.
The Expander - easy - What goes in small comes out big.
The Face That Breaks the Bank - medium - Roll enough dice and one number always runs away with it.
The Family Reunion - medium - Two cousins share a common ancestor somewhere above.
The Fast Climber - medium - Some routes up the mountain are faster than others.
The Field Counter - easy - Some fields speak louder than others.
The File Size Profiler - medium - File types and their disk footprint. One type dominates.
Roots and Branches - medium - Flat strings carry a hierarchy. Recover it.
The Fine Print - medium - Risk rules nest deep. Decide which transactions clear them.
The First Class Function - medium - Functions travel as values - prove you can pass one around.
The First Encounter - easy - Every character has a story - but only if you remember where it started.
The First Stranger - easy - In a crowd, the unique ones stand out first.
The Flat Mapper - medium - Nested values. One flat stream out.
The Forbidden Ceiling - easy - Round up. But not the obvious way.
The Forbidden Sorter - medium - Put the letters in order without the obvious tool.
The Forgetful Machine - medium - It remembers everything, until it does not.
The Forward Fill - easy - Patch the gaps in a noisy sensor stream.
The Frequency Eviction - hard - When storage is tight, something has to go.
The Gap Filler - easy - Fill the Nones with the last real value.
Roll Call - medium - The missing IDs in the log. Somebody has to notice.
The Gate Keeper - easy - Not all openings have a closing.
The Generous Ones - medium - The generous ones are obvious.
Above the Title - medium - Some names carry a genre. Total the box office behind them.
The Grid Pivot - easy - A different angle reveals a completely different picture.
The Half-Life Search - medium - Every guess cuts the problem in half.
The Halftime Score - easy - Middle value of a dataset. No built-in shortcuts.
The Hash Stamper - easy - One input, one irreversible output - the foundation of every secret.
Roots and Branches - hard - The chain of command arrives in pieces. Find where it begins.
The High Mark - easy - Scan the list. Report the max.
The High Rollers - medium - Not every gambler bets the same - some wager far more than others.
The Horizon Scanner - medium - For each position, what is coming up ahead?
The Hostile Takeover - medium - One dict eats another.
Under One Roof - medium - Some hosts have more to offer.
The Hourly Bucket - medium - Timestamps belong somewhere.
What's Left Standing - medium - They only meet head-on, and only mass decides who keeps going.
The Indivisibles - easy - Numbers that yield only to themselves.
The Infection Spread - hard - It starts with one, and then it spreads.
The Integer Sieve - easy - Not everything in this list belongs here.
The Intervals - medium - Timestamps in buckets.
Top-Heavy - medium - The widest row leads, and everything below it narrows.
The IP Validator - easy - Real and fake, mixed together.
The Island Counter - medium - Surrounded by water, connected by land - how many separate landmasses?
The Last Instance - easy - When duplicates appear, only the last one counts.
The Last Seen Map - easy - For each character, where did it appear last?
The Lazy Squares - easy - A sequence that never fully reveals itself.
The Lazy Stream - hard - Some slots hold one value, some hold a batch. Level them out.
The Lazy Unpacker - medium - Peel back every layer until only the values remain.
The Letter Census - easy - Every crowd has its share of talkers and quiet ones.
The Letter Frequency Map - easy - Count every character in the string and report the results.
The Letter Kin - medium - Words that share the same letters belong together.
The Letter Ledger - easy - Every character has a count to answer for.
The Letter Mapper - medium - A consistent substitution, or not.
The Letter Tally - easy - Each character in the string has a count to answer for.
The Level Inspector - medium - Each floor of the tower tells a different story.
The Level Summer - medium - Every tier of the hierarchy keeps its own total.
The Line Cutter - easy - Did everyone with an A-pass get through before the B-crowd arrived?
The Line Splitter - easy - Comma-separated truths, one at a time.
The Link Shrinker - medium - Long addresses have aliases - you give them out, you keep the map.
The List Merger - easy - No shortcuts.
Next in Line - medium - Every server gets its turn. Keep the line honest as the pool changes.
The Log Decoder - easy - Every line holds a secret.
The Log Pulse - easy - Some lines repeat themselves.
The Lone Character - easy - It appeared exactly one time. That made it special.
The Lone Traveler - easy - One character stands apart from the crowd.
The Low That Came Too Late - easy - You only get to buy before you sell. Find the biggest gain the day allowed.
The Long Way Around - easy - Anyone can call the function. Order it by hand.
The Map Reducer - medium - Map it. Reduce it. One answer.
The Market Streak - medium - Some stocks run longer than you think.
The Market Timer - medium - Buy low, sell later. The whole game is when.
The Matching Manifest - easy - Two warehouses, one shipment - only load what's in both.
Holding the Center - hard - The middle value keeps moving as new data arrives.
No Vacancy - hard - Every booking needs a room. Find the busiest moment.
The Merge - easy - Chaos in. Order out.
The Merge Champion - medium - Many sorted rivers flowing into one.
The Messy Pipeline - easy - The upstream API has no idea what a schema is.
The Middle Ground - hard - The middle value keeps moving.
The Min Tracker - medium - The stack remembers the best it ever saw.
The Minutes Tracker - easy - Some activities eat more time than others.
The Mirror Flip - easy - Sometimes the fastest fix is to swap everything.
The Mirror Image - easy - Flip the tape backwards - start from the end.
The Mirror Test - easy - Check if a string reads the same forwards and backwards.
The Mirror Words - easy - Each word looks back at itself.
The Missing Number - easy - Something is missing from the sequence.
The Molecule Report - easy - Four letters. A lot of math hidden in the sequence.
The Month-by-Month Snapshot - medium - Every salesperson has a story. The months just tell it sideways.
Higher Ground - medium - Somewhere the ground stops climbing.
The Multiplication Trail - easy - Each step multiplies the whole journey.
The Multiplier Rush - medium - Negatives cancel negatives - but only if you keep both in view.
The Narrow Lens - medium - A narrow timeframe. Everything inside matters.
The Nearest Value Mapper - medium - Close enough counts. Ties go low.
The Never-Ending Sequence - easy - Sequence that keeps going. Follow it.
The Numbered Chair - easy - A standing list. Position n holds one entry.
The Number Miner - medium - JSON strings are hiding numeric secrets - dig them out.
The Number Narrator - medium - Every number has a story in words.
The Number Screen - easy - Some numbers make the cut. Most do not.
The Odd Digits - easy - Hidden inside a mess of characters are a few odd numbers.
The Odd Extractor - easy - Not all numbers from a string are welcome here.
The Odd Filter - easy - Strip out everything that does not belong to the odd club.
The First of Their Kind - easy - When the same record arrives twice, only the first one survives.
The One-Timers - easy - Values that never repeated.
The One-Way Street - easy - Monotonic time-series. Direction only.
The Onion Layer - hard - Peel from the outside in - one ring at a time.
The Online Elite - medium - The top performers are hiding in the data.
The OOP Pillars Exam - medium - Four principles, one class hierarchy - show you know all of them.
The Op Dispatcher - easy - Name the operation, apply it everywhere.
The Order Enforcer - easy - Some rules say every A must come before every B.
The Order Inspector - medium - A binary tree has rules - is this one actually following them?
The Original Keeper - easy - Clean up duplicate events without losing the timeline.
The Output Peak - hard - One stretch outpaced all the others.
The Overlap Finder - easy - Two guest lists - who made it onto both?
The Overwritten Hour - medium - The log wrapped on itself. The order is still there, just not where you would look.
The Page Turner - medium - Nobody loads everything at once.
The Pair Counter - easy - How many pairs can be formed from the crowd?
The Paired Doors - easy - Every door you open is a promise to close it, in order.
Sum of Their Parts - medium - A stream of raw actions, folded into one portrait per person.
The Parentheses Factory - medium - Building balanced brackets is an art form.
The Pascal Row - easy - Each number is the sum of two numbers above it.
The Password Builder - easy - Random characters, fixed rules.
The Password Forge - easy - Does this password pass the strength gate?
The Pay Ladder - medium - Climb the ladder the hard way. No shortcuts allowed.
All the Way Down - medium - The payload nests without end. The warehouse needs one flat row.
The Peak Finder - easy - Largest number in the list. Max() is not an option.
The Perfect Match - medium - Two numbers walk into an interview...
The Pipeline Filter - easy - In the door as one thing, out the door as another.
The Placement Fixer - medium - Each value belongs in exactly one spot.
The Postfix Processor - medium - Math without parentheses - the operators come after the numbers.
The Precision Hunt - medium - Some answers need no decimal point.
The Price Bander - easy - Different prices, different treatment.
The Priority Queue - medium - When two things tie, something has to break the deadlock.
The Progress Meter - medium - Report progress at every tenth of the way through.
The Progress Parade - easy - Just tell them how far along you are.
The Quarter Turn - medium - One rotation changes everything.
The Queue Disguise - medium - A queue in sheep's clothing.
The Quiet Hours - medium - Overlapping outages hide how much time is really dark. Collapse them into the truth.
The Ranked Dict - easy - Values deserve order too.
The Record Reconciler - medium - Two versions of the same truth.
The Repeat Offenders - easy - Repetition is a clue.
The Repeat Review - medium - The echo came back.
The Repeat Visitor - medium - Loyal customers come back sooner than expected.
The Response Aggregator - medium - Multiple result pages. One clean summary.
The Resume Sifter - medium - Pull what's useful. Skip what you know.
The Rolling Peak - medium - The sweetest stretch in the sequence.
Steady State - medium - Turn a jittery stream into a calm read, one step at a time.
The Roman Converter - easy - Roman numerals decoded.
The Rotated Array - medium - Someone shuffled it. Now locate what you came for.
The Runner-Up - easy - Not the winner. The one just behind it.
The Running Total - easy - Each position holds the sum of everything before it.
The Safe Caster - easy - Type conversion is easy, until it is not.
The Schedule Cleaner - medium - Overlapping sessions. One clean line.
The Schema Diff - medium - Two versions of the same config - what changed between them?
The Schema Differ - medium - Schema from yesterday vs today. Something changed.
The Schema Migrator - hard - Old schema in, new schema out.
The Scoreboard Race - medium - The first to cross the line ends the game, mid-round or not.
The Score Sorter - easy - Points on the board, sorted by who earned the most.
The Scramble Check - easy - Same letters, different order - are these two strings secret twins?
The Second Summit - easy - Not the top of the mountain - just below it.
The Secret Twins - easy - Same letters, different disguises.
The Self-Portrait Number - easy - Some numbers describe themselves perfectly.
The Sequel Spotter - easy - Spot the sequels hiding in the catalog.
The Shadow Cleaner - easy - Remove the repeats. No shortcuts.
The Shape They All Share - medium - A pile of exports, no two quite alike. Keep only what every record agrees on.
The Shifting Standard - medium - A benchmark in motion.
The Short Address - medium - Every link needs a slug small enough to type by hand.
The Shortest Route - medium - Fewer hops is always better.
The Silent Locator - easy - Every lookup should cost you less than the one before it.
The Silver Screen Summit - medium - Box office totals decide who makes the top of the marquee.
The Single Bit - easy - One particular pattern hides in plain sight.
The Slow Leak - medium - Nested groups. One flat stream.
The Sneaky Twins - medium - They look different but they are the same inside.
The Social Graph - easy - Everyone knows someone.
The Solo Act - easy - One-and-done values only.
The Spin Doctor - medium - Ninety degrees, but which way?
The Spiral Harvest - medium - The snail reads the grid in its own special order.
The Spread - easy - Data spread around a center. The range matters.
The Squeeze - easy - aaabbb gets old fast. Shrink it.
The Staircase Problem - medium - One step or two, the choices add up.
The Status Board - medium - A pile of raw access logs, and two numbers that matter hiding inside the quotes.
The Step Counter - easy - You can hop one step or two - how many ways to reach the top?
The Streak Breaker - easy - It has a problem with repetition.
The Stream Averager - easy - The answer moves with the data.
The Stream Joiner - hard - Events don't wait for each other. This does.
The String Shrinker - easy - Compress the string. Shorter wins.
The Style Guide - easy - Not every word deserves the same treatment.
The Sum of Its Parts - medium - Somewhere in the stream, the deltas balance to your number. Count the runs that do.
The Sum of Its Parts - medium - Every assembly hides smaller ones. Count what it really takes to build.
The Syntax Sentinel - easy - Brackets opened and closed. The nesting might be off.
The Table Thief - medium - Somewhere in that query, tables are hiding.
The Tag Analyst - medium - Two sets of labels, one analysis.
The Tail End - easy - Push, pop, peek. The basics that break people.
The Tail Finder - medium - Navigate to the end of a linked list using recursion.
The Tail Trimmer - easy - Remove the k-th item from the back without counting forward first.
The Tallest Stacks - medium - Every terminal has its records. Find the two that stand tallest.
The Tally Counter - easy - How many times does a single guest show up to the party?
The Target Hunt - medium - Pairs that hit a target. Every one of them.
The Throttle Ceiling - medium - Too many requests in too short a timeframe. Throttle it.
The Throttle Wall - hard - Stop the abusers. Let the rest through.
The Timezone Trap - medium - Trip data and timezones. They're not the same thing.
The Timing Decorator - medium - Wrap any function to capture how long it takes.
The Title Ladder - medium - Job titles and the salary tier they belong to.
The Top Reviewer - easy - One restaurant receives the most feedback - which one?
The Top Words - medium - In every document, some words dominate the conversation.
Footprints in the Feed - medium - Every trade left a footprint.
The Trade Signal - easy - Buy low, sell high. Identify the ideal moment.
The Traffic Director - easy - Spread the load evenly - nobody should be doing all the work.
The Trapped Pool - hard - What collects in the valleys after the rain?
The Tree Measurer - easy - How deep does the rabbit hole go?
The Trip Aggregator - medium - Travel records hold patterns waiting to be surfaced.
The Trip Grouper - easy - Where did everyone go, and for how long?
The Triple Alliance - hard - Three numbers, one target.
The Triplet Hunt - medium - Every path that works gets a seat at the table.
The Type Sorter - easy - A mixed list is hiding its numbers - extract them.
The Value Sorter - easy - The order was always negotiable.
The Velvet Rope - medium - Some users get in. Others wait outside until the window resets.
The Version Parade - easy - 1.0 before 2.0. Don't let the dots confuse you.
The Version Ranker - medium - Software versions follow their own ordering rules.
The Vocabulary Test - medium - Every character has to come from a word you already know.
The Vowel Hunt - easy - Just the vowels. All of them.
The Waiting Game - medium - Patience has a price - and a count.
The Water Collector - hard - Two walls, one sky, and a very important question.
The Water Gauge - medium - Elevation bars trap water between peaks - count the volume.
The Weight of the Book - medium - Every holding pulls its weight. Order the asset classes by what they carry, and let the ties settle by name.
The Window Cleaner - medium - Keep it fresh, keep it unique.
The Word Census - easy - Who said what - and how many times?
The Word Counter - easy - How many times does each word show up in a file?
The Word Families - medium - Different spellings, same letters - they belong together.
The Word Flipper - easy - The sentence stays, the words surrender.
The Word Inventory - easy - Every word, twice over.
The Word Map - easy - Language, quantified.
The Word Mismatch - easy - Some text does not match.
The Yahtzee Engine - hard - Five dice. Six faces. Score it.
The Yahtzee Scorer - medium - Dice scoring. Multiple categories evaluated.
The Zero Propagator - medium - One zero can change the whole picture.
The Zigzag Encoder - medium - The message snakes its way across the rails.
Threshold Filter - medium - Above the line or below it.
The Spaces Between - easy - Raw lines arrive padded and uneven. Recover the fields that matter.
Top N Keys - medium - Most of them do not matter. The few that do stand out.
Transform Column - easy - Same data, new shape.
Against the Grain - medium - Turn the grid on its side and let every column stand up as a row.
Three That Hold - medium - Not every triangle is a triangle.
Type Caster - easy - Wrong type. Fix it.
Unbroken - easy - A single dip resets the clock. Find the longest the machine held over the line.
Hidden Depths - medium - Each dot marks a level. Rebuild the tree it stands for.
Unique Values - easy - Duplicates are noise. Remove them.
Validate Email - medium - Looks like an email. But is it?
Value Count - easy - How many of each? Count them.
Ways of Reading - medium - One key, no separators, and more than one story it could tell.
When the Hours Touch - medium - Two sessions that overlap are really one. Find the windows a driver was actually online.
Word Counter - easy - Words in, counts out.
Zip to Record - easy - Two lists become one record.