What level of Python is expected for an entry-level data engineer role?

Read a CSV with csv.DictReader, deduplicate by single key using a dict, parse a JSON file, write a generator for streaming. Basic dict and set operations. Handle empty input and missing fields gracefully. Vanilla Python preferred; pandas allowed when appropriate but rarely required at this level. No need for asyncio, generators-of-generators, or context manager protocols.

Do I need to know data modeling at entry-level?

Yes, at a foundational level. Fact vs dimension distinction, basic star schema (one row per X grain, dim_customer, dim_product, dim_date), SCD Type 1 (overwrite) vs SCD Type 2 (new row per version with effective dates) reasoning. The interview will not test data vault or medallion architecture at L3; it will test whether you can pick a grain and defend it.

What is the Python coding bar like at L3 versus L5 data engineer?

L3 bar: correct, clean, readable solution that handles obvious edge cases. The interviewer wants to see you can structure code, name things clearly, and not silently fail on malformed input. L5 bar: same plus complexity reasoning, library familiarity (pandas, polars, asyncio, tenacity), and trade-off articulation (dict vs sort-and-iterate, generator vs list, when async vs sync).

Do entry-level data engineer candidates need to know AWS or GCP?

Helpful but not blocking. Most L3 rounds focus on language fluency (SQL, Python) and basic data modeling. Cloud-specific questions appear in design rounds, which are rare at entry-level. Knowing the basics (S3 or Cloud Storage for object storage, Redshift or BigQuery for warehouse, basic ETL service names) is enough; deep operational knowledge is L5+ territory.

How do interviewers calibrate at the entry level?

On trajectory more than on accomplishment. Interviewers know L3 candidates have not shipped 10 years of pipelines; they are looking for learning velocity (how quickly do you pick up a new pattern when shown one), ownership (do you take responsibility for your code's correctness or hand-wave), and communication (can you talk through your thinking clearly). Specific numbers in stories matter even for short tenure.

Entry-Level Data Engineer Interview Questions (Junior, L3-L4 Bar)

Entry-Level Data Engineer Interview Questions

Junior-level data engineer interview questions with live execution.

Entry-level data engineer interview questions filtered from the catalog. Foundational SQL (joins, aggregation, simple window functions). Python parsing and dict work. Fact-versus-dimension modeling. The bar is correctness and communication; entry-level interviewers want clean reasoning, not advanced trade-offs.

Entry-level (L3, sometimes L4 floor) data engineer interview rounds test foundational fluency, not advanced patterns. The SQL bar is JOIN (INNER, LEFT, with WHERE-versus-ON correctness), GROUP BY with HAVING, basic window functions (ROW_NUMBER for top-N per group, RANK and DENSE_RANK for ties, simple SUM OVER for running totals; frame clauses are rarely tested at L3), and CTEs as readability tools. The Easy tier of the catalog is calibrated for 5-to-10-minute solve times for a fluent junior data engineer candidate. The Medium tier is calibrated for 10-to-15-minute solve times. Hard problems (gap-and-island, sessionization, recursive CTE) are out of scope for entry-level loops.

The entry-level data engineer Python round is pipeline-shaped but with simpler prompts. Read a CSV with csv.DictReader. Deduplicate by single key using a dict. Parse a JSON file with json.load. Write a generator that yields rows from a large file. Implement basic dict and set operations. The catalog covers each. The bar is not a clever one-liner; it is a clear, correct, readable solution that handles the obvious edge cases (empty input, missing fields, malformed lines should go to a dead-letter list).

The entry-level data engineer modeling round tests fact-versus-dimension understanding, basic star schema design (one row per X grain, dim_customer, dim_product, dim_date), and simple SCD Type 1 versus Type 2 reasoning. Pipeline architecture is rare at entry-level and, when it appears, tests the basic shape (source to ingest to transform to warehouse to BI tool) rather than failure modes. Behavioral rounds emphasize learning velocity, ownership, and collaboration; interviewers know entry-level candidates will not have 10 years of project examples and are calibrating on the trajectory.

Entry-level data engineer candidates do not need deep cloud expertise. Knowing the basics (S3 or Cloud Storage for object storage, Redshift or BigQuery for warehouse, basic ETL service names) is enough. Deep operational knowledge (DISTKEY tuning on Redshift, slot reservations on BigQuery, AQE configuration on Spark) is L5+ territory.

The L3-versus-L4 distinction for data engineer roles. L3 expects clean foundational solutions and learning trajectory. L4 expects the same plus initial trade-off articulation (I picked dict because it is O(1) lookup versus O(n) for a list search), basic edge-case handling without prompting, and basic design familiarity (can you sketch a high-level pipeline for a simple scenario). The jump from L3 to L4 is about reflexive engineering hygiene, not about advanced patterns.

Prep priorities for an entry-level data engineer interview with 4 weeks. Week 1-2: SQL fundamentals (JOIN, GROUP BY, ROW_NUMBER, CTEs). Solve 40-60 Easy and Medium problems. Week 3: Python pipeline patterns (CSV parsing, dedup, generators). Solve 20-30 problems. Week 4: data modeling drills (star schema for 3-4 different domains), 1-2 behavioral rounds with someone, and a timed mock for each round type. Do not try to learn advanced patterns (sessionization, recursive CTE) at L3; depth over breadth on the foundations.

SQL interview questions (start with Easy tier) - 922 problems; the Easy tier is calibrated for junior data engineer fluency.
Python interview problems (foundational) - Parsing, dedup, dict work; the patterns junior data engineer rounds test.
SQL JOIN problems (foundational) - INNER, LEFT, WHERE-vs-ON correctness.
SQL aggregation problems (foundational) - GROUP BY, HAVING, COUNT vs COUNT DISTINCT.
Window functions (start with ROW_NUMBER) - ROW_NUMBER for top-N per group; the entry-level window-function bar.
Data modeling at the entry level - Fact vs dimension, star schema, SCD Type 1 vs Type 2.
Junior data engineer interview prep - Round-by-round prep for L3-L4 candidates.
Data engineer roadmap - What to learn first, what to learn next, in what order.
Data engineer career path L3 to L7 - What changes at each level, what to focus on first.

What is the SQL bar at entry-level data engineer interviews?: Foundational fluency: JOIN (INNER, LEFT, with correct WHERE-vs-ON predicate placement), GROUP BY with HAVING, basic window functions (ROW_NUMBER for top-N per group, RANK/DENSE_RANK for ties, simple SUM OVER for running totals), and CTEs as readability tools. Frame clauses (ROWS BETWEEN N PRECEDING) are rarely tested at L3. Hard patterns (gap-and-island, sessionization, recursive CTE) are out of scope.
What level of Python is expected for an entry-level data engineer role?: Read a CSV with csv.DictReader, deduplicate by single key using a dict, parse a JSON file, write a generator for streaming. Basic dict and set operations. Handle empty input and missing fields gracefully. Vanilla Python preferred; pandas allowed when appropriate but rarely required at this level. No need for asyncio, generators-of-generators, or context manager protocols.
Do I need to know data modeling at entry-level?: Yes, at a foundational level. Fact vs dimension distinction, basic star schema (one row per X grain, dim_customer, dim_product, dim_date), SCD Type 1 (overwrite) vs SCD Type 2 (new row per version with effective dates) reasoning. The interview will not test data vault or medallion architecture at L3; it will test whether you can pick a grain and defend it.
What is the Python coding bar like at L3 versus L5 data engineer?: L3 bar: correct, clean, readable solution that handles obvious edge cases. The interviewer wants to see you can structure code, name things clearly, and not silently fail on malformed input. L5 bar: same plus complexity reasoning, library familiarity (pandas, polars, asyncio, tenacity), and trade-off articulation (dict vs sort-and-iterate, generator vs list, when async vs sync).
Do entry-level data engineer candidates need to know AWS or GCP?: Helpful but not blocking. Most L3 rounds focus on language fluency (SQL, Python) and basic data modeling. Cloud-specific questions appear in design rounds, which are rare at entry-level. Knowing the basics (S3 or Cloud Storage for object storage, Redshift or BigQuery for warehouse, basic ETL service names) is enough; deep operational knowledge is L5+ territory.
How do interviewers calibrate at the entry level?: On trajectory more than on accomplishment. Interviewers know L3 candidates have not shipped 10 years of pipelines; they are looking for learning velocity (how quickly do you pick up a new pattern when shown one), ownership (do you take responsibility for your code's correctness or hand-wave), and communication (can you talk through your thinking clearly). Specific numbers in stories matter even for short tenure.
What should I focus on first if I have 4 weeks to prep for an entry-level data engineer interview?: Week 1-2: SQL fundamentals (JOIN, GROUP BY, ROW_NUMBER, CTEs). Solve 40-60 Easy and Medium problems. Week 3: Python pipeline patterns (CSV parsing, dedup, generators). Solve 20-30 problems. Week 4: data modeling drills (star schema for 3-4 different domains), 1-2 behavioral rounds with someone, and a timed mock for each round type. Do not try to learn advanced patterns at L3; depth over breadth on the foundations.
What is the difference between L3 and L4 data engineer bars?: L3 expects clean foundational solutions and learning trajectory. L4 expects the same plus initial trade-off articulation ('I picked dict because it is O(1) lookup vs O(n) for a list search'), basic edge-case handling without prompting, and basic design familiarity (can you sketch a high-level pipeline for a simple scenario). The jump from L3 to L4 is about reflexive engineering hygiene, not about advanced patterns.

666 practice problems matching this filter. Domains: SQL (478), Data Modeling (2), Python (186). Difficulty: easy (431), medium (225), hard (10).

SQL (478)

30-Day Page View Counts - easy - Thirty days of engagement. Quick snapshot.
Above Average - easy - Products beating the catalog average.
Where the Money Burns - medium - Some services quietly burn more than the rest.
Active API Tokens - easy - Tokens that have actually been used.
Active Campaigns - easy - Which campaigns are earning their keep?
Active Searchers - medium - They typed a query. That means something.
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 Revenue for April - easy - Total revenue from active users in a single month
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 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.
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.
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 Calls With and Without Errors - medium - Some calls succeed. Some do not. Break it down.
API Token Churn Rate - medium - Tokens come and go. What's the turnover?
April and May Active Users - easy - Spring cleaning for the user base. Who was actually around?
Attributable Impression Rate - medium - What share of ad impressions can be traced to a real user account
Auth Endpoint Callers - medium - Identify users who have called authentication API endpoints
Auth Endpoints - easy - Not all endpoints are visible to everyone.
Authors With Successful Deploys - easy - Who deployed successfully?
Auth Service Health Checks - easy - One service. Full audit trail.
Average API Latency by Year - medium - Latency year over year. Is it getting better?
Average Brand Campaign Revenue - easy - A quick benchmark on brand campaigns.
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 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?
Average Initial Call Latency - medium - First contact latency. The benchmark.
Average Latency by Health Status - easy - Healthy versus degraded. The latency gap is real.
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
Average Update Call Latency - medium - Follow-up calls. How fast?
Average Watch Time by Format - medium - Which content format keeps viewers watching the longest
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.
Big Spenders - easy - The whale list.
Binary Flag Indicators - medium - On or off. Every flag at a glance.
Bottom Endpoints by POST Volume - medium - The quietest POST endpoints.
Bronze Medal - easy - Two ahead of you. The rest below.
Budget-Friendly Products - easy - Affordable does not mean invisible.
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.
Busy Authors - medium - Some developers spread their commits everywhere.
Campaign Cost Effectiveness - medium - Money in, conversions out. What is the ratio?
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.
Category Census - easy - Which aisles are worth restocking?
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.
Character Position in Endpoint - easy - URL patterns, character by character.
Chat Activity - easy - Which channels are ghost towns?
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.
Clean Averages - easy - Merchandising only cares about the categories customers actually rate.
Clean Cache CDN Edges - easy - Cached, clean, error-free edges.
Clicked Ad Impressions - easy - They saw the ad. They clicked.
Loyalty's Double Tap - medium - When a nudge and a banner team up.
Click Rate - medium - Campaigns nobody clicks.
Click Revenue - easy - Which campaigns are earning their keep?
Cloud Bill - easy - Which cost buckets are bleeding money?
Cloud Cost by Team - easy - Spend by team. Who's burning most?
Cloud Cost Stats by Provider - medium - Three providers. Three very different bills.
Common Age Buckets - easy - Duplicate records hiding in the users table.
Completed Priority-1 Jobs - easy - Priority one. Completed.
Compute Nodes in Key Regions - easy - Compute nodes across the key regions.
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 Published in 2026 - easy - Published back then. Still relevant?
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 Efficiency Ratio - easy - Dollars in, value out. What's the ratio?
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?
Customer Full Name Concat - easy - First name, last name. Combine them.
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 Session and User Counts - medium - Sessions and users, day by day.
Data Repo Fix Commits - medium - How many commits start with 'fix'?
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 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.
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.
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.
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.
Distinct Product Categories - easy - A quick category inventory.
Diverse Shoppers - medium - They shop the whole catalog.
Duplicate DQ Check Records - 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 2026 Data Pipelines - easy - Early-year data pipelines.
Efficient Pipeline Throughput - medium - Throughput per pipeline. The benchmark.
Email Census - easy - The reachability split.
Engagement by Content Type - medium - Some content types get all the attention.
Error Hall of Fame - medium - The year's worst error categories.
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.
Exact Keyword Counts in Logs - hard - Errors and warnings. Count every single one.
Expensive AWS Services - easy - Some AWS services quietly drain the budget.
Extreme Headcount Departments - easy - The pay extremes tell a story.
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.
Fastest CI Build Date - medium - The fastest build ever. When did it happen?
Fastest Regions by Latency - medium - The fastest regions. Benchmarked.
Feature Flag Adoption - medium - How widely adopted are the flags?
Features With Missing Values - easy - Missing data in the features.
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 Deploy Authors - easy - Same person. Many different spellings.
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.
First Migration Record - easy - The very first migration. Where it all began.
First Touch Attribution - medium - The first interaction matters most. Or does it?
Flag Check - easy - Which flags are actually live?
Frequent Message Senders - medium - Someone is sending too many messages.
Friday Spending Analysis - hard - Friday spending during Q1.
Full Customer Order List - easy - Every customer. Every order. The full picture.
Gateway Connection Timeouts - easy - Timeouts at the gateway.
Health Check Distribution - easy - Pass, fail, degraded. The distribution.
Health Checks per Service - easy - Some services get checked constantly.
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.
High and Critical Alerts in 2026 - easy - High and critical alerts from that year.
High Engagement Pages - hard - Some pages hold attention longer than others.
Higher Performing Variant - easy - Control versus treatment. One wins.
Highest and Lowest Cloud Costs - medium - The extremes in cloud spending.
Highest Cost Per Team - easy - Peak cost, team by team.
Highest Latency Endpoints - easy - The slowest endpoints. Everyone notices.
Highest Throughput Pipelines - medium - The pipes that carry the most water.
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-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?
Impressions by Search Keyword - hard - Campaign performance, keyword by keyword.
Inactive Android Control Users - medium - Android control cohort. Gone quiet.
Inactive Unverified Users - easy - Signed up. Never verified. Never came back.
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.
iOS Sessions by Device Type - medium - iOS engagement, device by device.
Japan Revenue for April - easy - Last month's numbers for one region.
The Row Count Surprise - easy - Same tables. Different handshakes. Wildly different results.
Largest A/B Test by Participants - medium - The biggest experiment ever run.
Largest Single Cloud Cost - medium - One line item. The biggest bill of all.
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 Variance and Std Dev - hard - How much does latency actually vary?
Latest Metric Values - easy - Stale records hiding in the metrics.
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?
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 Running Pipeline - medium - One pipeline outlasted them all.
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
Lowest Average Price Category - easy - The cheapest category. Not necessarily the worst.
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.
Active Token Owners in 2026 - easy - Active token owners this year.
Memory-Heavy Pods - easy - Memory-hungry workloads.
Message Length - 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 Value Pairs Over Threshold - medium - Two metrics, both above the line.
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.
Mid-Tier Batch Jobs - 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.
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.
Models With Variable Accuracy - medium - Accuracy should be stable. These models are not.
Model Training Completion Rate - medium - How many models finished training?
Monthly Active Users per Endpoint - easy - One endpoint, many users. Which ones showed up?
Thirty Days of Shipping - easy - A month in the life of an engineering team, counted one deploy at a time.
Monthly Revenue Comparison - medium - Last month versus this month. Per product.
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.
Monthly Unique Users per Campaign - easy - Monthly reach, campaign by campaign.
Month With Fewest Deploys - medium - One month, nobody deployed.
Morning Warning Logs - easy - Warnings before noon.
Most Active Recent Committers - medium - Who has been writing the most code lately?
Most Active Servers by Log Volume - medium - The busiest servers by log volume.
Most Common Export Job Status - easy - The most common job status.
Most Common Monday Outcome - medium - Mondays have a pattern.
Most Frequent Error Types - medium - The errors that keep coming back.
Most Popular Content Type - medium - The content type everyone prefers.
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-Provider Cost Lookup - easy - AWS, GCP, Azure. Side by side.
Multi-Variant Experiments - easy - One user, multiple experiments.
Net Lines - medium - Some authors build. Others trim. The net tells the truth.
Never-Ordered Products - easy - In the catalog. Never purchased.
New User Purchases - medium - What's this year's signup cohort worth so far?
Nodes by Region and Type - medium - Broken down by region. Broken down by type.
Nodes in Key Regions - medium - Six regions. How many nodes in each?
Nodes in Target Regions - easy - The target regions need attention.
Node Summary Per Region - easy - Every region has a node story.
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.
Notification Delivery Ratio - medium - Sent versus delivered. The gap is the problem.
Did Anyone Actually Read It? - easy - A push isn't a win until a thumb taps it.
The Vanishing Rows - easy - Some records disappear when the tables meet. Figure out why.
The Scorched Earth Reviews - easy - Someone was unhappy. Find out how many times.
Opened Notifications in Jan-Feb - medium - Two months of push notifications. How many were actually read?
Overall Average API Latency - easy - The overall average. Across everything.
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 Ad Revenue Moment - easy - The single peak earning moment.
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 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 Recovery by Priority - medium - Recovery time, priority by priority.
Pipeline Run History - easy - The lineage trail.
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.
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.
Price Check - easy - Priced to sell or priced to sit?
Shipped to Prod - easy - Staging is safe. Production is real. How many made the jump?
Production Deploys From April Onward - easy - After the cutoff, how many times did prod get a push?
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.
Promo Campaign Cost per Acquisition - easy - The campaign ran. What did each customer cost?
Purchase Log - easy - Names on receipts, not just IDs.
Push Opens by Platform and Campaign - medium - Opens by platform and campaign.
Q2 Search Volume - easy - Q2 search volume. The numbers.
Q by Q - easy - Thirteen weeks. This is how the team spent them.
Rate Limit Rules Per Endpoint - medium - Threshold rules, endpoint by endpoint.
Recurring Error Types - easy - The same errors, recurring.
Regional Order Summary - medium - Region by region. The order numbers tell the story.
Regional Profits - easy - P&L by region. Before the board meeting.
Regional Status - easy - The full regional breakdown.
Regions by Alert Volume - medium - Some regions are quiet. Others never stop screaming.
Regions With 5+ Nodes - easy - Regions with five or more nodes.
Region With Best Uptime - medium - The single most reliable region.
Region With Most Nodes - medium - Which region hosts the most?
Resolved vs Unresolved Alerts - hard - Resolved versus open. By severity.
Retargeting Campaign Impressions - easy - Retargeting impressions. All of them.
Revenue by Product - easy - Which products carry the revenue line?
Revenue Per Product With Zeros - medium - Total revenue per product. Even the zeros.
Reviews Per Reviewer - easy - The workload split across reviewers.
Runner-Up Cost Without ORDER BY - medium - The second highest. Without sorting.
Rush Hour API Latency - medium - Rush hour hits the API differently.
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 Terms Starting With G - easy - Queries starting with 'g'.
Second Highest Cloud Cost - medium - The second biggest bill on record.
Second Highest Salary - easy - Silver medal. Almost the top, but not quite.
Second Highest Value - easy - Almost the top. Not quite.
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 Component Classification - medium - Classified by naming pattern.
Services With Most Error Occurrences - easy - The noisiest services.
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 Pulse - easy - Engagement is slipping. Who is phoning it in?
Sessions by Content Type - medium - Engagement, broken down by content format.
Sessions Per Device Type - easy - Sessions, device by device.
Shared Endpoints - medium - Shared credentials across endpoints.
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.
Signups Jan to Jul 2026 - easy - Signups from January through July.
Single Service Owners - medium - One owner, one service. Nobody else.
Sirens and Smoke - easy - Stale alerts. Still ringing.
Slow Failures - easy - SRE is hunting for the endpoints that fail slowly enough to burn timeouts.
Slow Production Deploys - easy - Production deploys that took way too long.
The Compliance Order - easy - Token scopes need to be in the right sequence before the audit.
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.
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.
The Ad Ledger - easy - Annual ad revenue. On the record.
The Campaign Trail - easy - Impressions are vanity. Conversions are sanity.
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 Legacy Hunt - easy - Old data. Still matters.
The Publishing Audit - easy - Published years ago. Still generating views?
The Quiet Alarms - medium - Low severity. High volume. Worth a look.
The Token Census - easy - How many tokens are out there?
Third Largest Batch Job - easy - Bronze medal in the batch job rankings.
Threads Excluding User - easy - Every thread they're not part of.
Three Lowest Distinct Cloud Cost Amounts - easy - The three cheapest bills on record.
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.
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 2 Active Push Days - medium - Two days stood out from the rest. Which ones?
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.
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 Ad Campaigns by Revenue - easy - Every campaign has a bottom line. Stack them up.
Top Alert Resolvers - medium - The engineers who resolve the most.
Top API Caller - medium - One user triggered more API calls than anyone.
Top Batch Job Under Priority 1 - medium - Priority one. Top performer.
Top Cost Categories - medium - Three categories eating the budget.
Top Cost Entry per Team - medium - The single biggest bill per team.
Top Deployed Model - easy - The best-performing model in production.
Top Device by Sessions - easy - One device type generates the most sessions.
The Loudest Failures - medium - Twelve months of errors. Which types showed up most?
Top Five - easy - The five priciest items for the luxury section.
Top Metric Values - easy - The five highest numbers. No duplicates.
Top Mobile OS by Session Duration - easy - Which mobile OS keeps users longest?
Top Performing Models - easy - The models that actually perform.
Top Product Categories by Sales - easy - The highest-grossing categories.
Top Products by Quantity Sold - medium - The bestsellers. By volume.
Top-Ranked Wines by Variety - easy - The best bottles. Ranked by variety.
Top Region by Order Volume - medium - The single busiest region.
Top Repos by Successful Builds - medium - Green builds. Which repos lead?
Top Services by Regional Cost - medium - Top spenders in one region.
Top Shelf - easy - Buyers need to know ceiling prices before negotiating with vendors.
The Spender Leaderboard - easy - Spending speaks. The leaderboard does the listening.
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 Rows by Pipeline Status - easy - Row counts alongside pipeline aggregates.
Total User Spend - easy - Each customer's total. Summarized.
Transaction Overview - easy - The executive snapshot. Users, products, revenue.
Transaction Revenue by Customer - medium - One month, every customer, every dollar accounted for.
Transaction Source Features - easy - One pipeline reviewed them. What did it see?
Transaction Timeline - medium - First purchase to last. The full spending arc.
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 Hosts by Node Type - easy - How many unique hosts per node type?
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.
Unused Read Tokens - easy - Active tokens that nobody uses.
US-East KV Store Entries - easy - KV store inventory. us-east-1.
User Age Ranking - easy - Age brackets, stacked from top to bottom.
User Devices - medium - Desktop, mobile, tablet. What does each user actually use?
User Engagement Summary - medium - Sessions plus searches. The full engagement picture.
User Engagement Totals - easy - Per-user engagement. The totals.
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 Per Device Type - easy - Users per device. The split.
Users Who Clicked Ads - easy - Ad clickers and their account details.
Users With Admin Tokens - medium - Admin tokens. Who holds them?
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.
Verify Commit ID Uniqueness - easy - Duplicate commit IDs. Are there any?
View Count Per Page - easy - Every page has visitors. Some just have more.
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 Transaction Volume - easy - Weekly volume. The pulse.
Welcome Wagon - easy - How many signed up this year?
Whale Watch - easy - The accounts driving the top line.
Word Count Per Message - medium - How wordy are the messages?
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.

Data Modeling (2)

A Number for the Seller - easy - They want a total. Give them the right schema first.
Event Ticketing System Data Model - easy - JSON in. Reporting warehouse out. Design both ends.

Python (186)

Batch Records - medium - Too many at once. Break them into groups.
Batch With Metadata - easy - The list gets chopped.
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.
Cumulative Sum - medium - The total grows with every row.
Detect Cycle in Sequence - medium - Follow the chain long enough and it might loop back.
Dominant Element - easy - Majority element. Appears more than half the time.
Even Filter - easy - Only the even ones survive.
Explode List - easy - One row holds many values. Unpack it.
Extract Domain - easy - The domain is buried in the string.
Find Indices - medium - It is in there somewhere. Where exactly?
Find Mode - medium - One value appears more than the rest.
Flatten the Feed - easy - Nested lists, all the way down.
Greeting Formatter Class - easy - First impressions are formatted carefully.
Group By - medium - Same key, different rows. Bring them together.
Lag Column - medium - What came before this row?
Max Length Token - medium - The longest token wins.
Merge Counters - medium - Two tallies. Combine them.
Normalize Name - easy - Names are messy. Standardize them.
Null Counter - easy - How many holes in the data?
Quality Gate - easy - Not everything passes inspection.
Points of Order - medium - Every page makes its case for the top. Settle it, and settle the ties.
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.
Row Aggregates - medium - Each row holds its own summary.
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.
Sort Descending - easy - Biggest first. No exceptions.
Stock Range Finder - medium - Prices move. One stretch had the widest gap.
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 Balanced Sum - easy - Some numbers have a rare quality that mathematicians revere.
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 Bitwise Judge - easy - No division, no modulo - just a single bit tells you everything.
The Bonus Round - medium - Consecutive matching dice rolls trigger a special scoring rule.
The Bouncer - easy - Every door has a guest list.
The Bronze Medalist - easy - Not first, not last - somewhere in the middle of the podium.
The Bug Spotter - easy - It compiles. The answer is still wrong.
The Calendar Sort - easy - Time has its own opinion about order.
The Carousel - easy - Keep moving, same ride.
The Chain Builder - medium - Links connect in sequence - build the chain from scratch.
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 Character Encoder - easy - Squeeze a string down to its tightest form.
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.
The Clock Angle - 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 Column Transformer - easy - Each column gets its function.
The Roll Call - easy - Every value is waiting for its name.
The Config Blender - easy - Config collision. The surviving values after a merge.
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 Cycle Detector - medium - Follow the chain long enough and you might end up where you started.
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 Unpacker - easy - Boxes inside boxes. Eventually you reach the bottom.
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 Dominant Signal - easy - Hottest items in the transaction log. Ties included.
The Duplicate Spotter - easy - Some values appear more than once - report only those.
The Elevator Trace - medium - Nested floors. One path through.
The Email Ranker - medium - Some inboxes see more action.
The Even Checkpoint - easy - Is this number in the even club? Prove it the fast way.
The Exception Handler - medium - Good code handles failure as gracefully as success.
The File Size Profiler - medium - File types and their disk footprint. One type dominates.
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 Forward Fill - easy - Patch the gaps in a noisy sensor stream.
The Generous Ones - medium - The generous ones are obvious.
The Grid Pivot - easy - A different angle reveals a completely different picture.
The Hash Stamper - easy - One input, one irreversible output - the foundation of every secret.
The High Mark - easy - Scan the list. Report the max.
The Host Ranker - medium - Some hosts have more to offer.
The Integer Sieve - easy - Not everything in this list belongs here.
The Intervals - medium - Timestamps in buckets.
The Inverted Triangle - medium - A pattern of stars narrows toward the bottom.
The IP Validator - easy - Real and fake, mixed together.
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 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 Tally - easy - Each character in the string has a count to answer for.
The Level Summer - medium - Add up each level of the tree.
The Line Cutter - easy - Did everyone with an A-pass get through before the B-crowd arrived?
The Log Pulse - easy - Some lines repeat themselves.
The Lone Traveler - easy - One character stands apart from the crowd.
The Map Reducer - medium - Map it. Reduce it. One answer.
The Market Timer - medium - One buy, one sell - when do you make the most?
The Matching Manifest - easy - Two warehouses, one shipment - only load what's in both.
The Merge - easy - Chaos in. Order out.
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 Multiplication Trail - easy - Each step multiplies the whole journey.
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 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 One-of-Each - easy - Strip the repeats, keep the originals.
The One-Way Street - easy - Monotonic time-series. Direction only.
The OOP Pillars Exam - medium - Four principles, one class hierarchy - show you know all of them.
The Order Enforcer - easy - Some rules say every A must come before every B.
The Original Keeper - easy - Clean up duplicate events without losing the timeline.
The Overlap Finder - easy - Two guest lists - who made it onto both?
The Pair Counter - easy - How many pairs can be formed from the crowd?
The Paired Doors - easy - Every open bracket has a partner - but not every partner shows up.
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 Payload Flattener - medium - Turn a deeply nested API response into a flat row.
The Peak Finder - easy - Largest number in the list. Max() is not an option.
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 Ranked Dict - easy - Values deserve order too.
The Repeat Review - medium - The echo came back.
The Response Aggregator - medium - Multiple result pages. One clean summary.
The Resume Sifter - medium - Pull what's useful. Skip what you know.
The Roman Converter - easy - Roman numerals decoded.
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 Scoreboard Race - medium - Simulate rounds until someone hits the target.
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 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 iterators. One flat stream.
The Social Graph - easy - Everyone knows someone.
The Solo Act - easy - One-and-done values only.
The Squeeze - easy - aaabbb gets old fast. Shrink it.
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 Style Guide - easy - Not every word deserves the same treatment.
The Syntax Sentinel - easy - Brackets opened and closed. The nesting might be off.
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 Tally Counter - easy - How many times does a single guest show up to the party?
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 Tree Measurer - easy - How deep does the rabbit hole go?
The Trip Aggregator - medium - Travel records hold patterns waiting to be surfaced.
The Type Sorter - easy - A mixed list is hiding its numbers - extract them.
The Value Sorter - easy - The order was always negotiable.
The Version Ranker - medium - Software versions follow their own ordering rules.
The Vowel Hunt - easy - Just the vowels. All of them.
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 Flipper - easy - The sentence stays, the words surrender.
The Word Mismatch - easy - Some text does not match.
The Yahtzee Scorer - medium - Dice scoring. Multiple categories evaluated.
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.
Type Caster - easy - Wrong type. Fix it.
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.
Word Counter - easy - Words in, counts out.
Zip to Record - easy - Two lists become one record.