Your day job does not prepare you for what they actually ask in the interview. Practice the real rounds. Find your gaps before the interviewer does. Free forever.
DataDriven is a 100% free data engineering interview prep platform. Practice 2,000+ SQL, Python, data modeling, and pipeline architecture challenges with real code execution against live PostgreSQL databases. No trial, no credit card, no catch.
Skills You Will Practice
SQL
The queries interviewers actually write on the whiteboard. Appears in 95% of DE interviews.
JOINs, self-joins and subqueries
Window functions
CTEs and recursive queries
Aggregations
NULL handling
Date functions and time series
Data Modeling
The interview round that separates analysts from engineers. Appears in 65% of DE interviews.
Schema design and normalization
Star and snowflake schemas
Slowly changing dimensions
Entity relationships and cardinality
Keys, constraints and indexing
Design patterns and trade-offs
Python
The data transforms and pipeline logic interviewers test. Appears in 78% of DE interviews.
Dictionaries and deduplication
List comprehensions and filtering
String slicing and time bucketing
Event stream processing
Idempotent data transforms
Aggregation without pandas
Pipeline Architecture
Design the systems that move data at scale. Appears in 52% of DE interviews.
Scheduling and orchestration
Batch vs streaming
Data quality and validation
Idempotent pipelines
Schema evolution
Monitoring and alerting
Platform Features
Adaptive Difficulty: DataDriven escalates you toward interview-level difficulty based on your actual performance, not your comfort zone.
Readiness Score: Track coverage across every concept interviewers test. When it is green, you are ready.
Company-Specific Prep: Filter to exactly what your target company asks, by role and level.
Spaced Repetition: Concepts surface again right before you would forget them. Nothing slips.
Real Code Execution: Your code runs against real datasets. No multiple choice. Write a query, run it, see if your output matches. Row by row.
How DataDriven Works
Focus: Define your target companies and level. DataDriven cuts the scope of your focus areas by up to 60%, stripping away the noisy things interviewers do not ask.
Sharpen: Every challenge narrows in on the area that optimally improves your interview success rate, so every minute that you spend is impactful.
Practice: Master the SQL, Python, data modeling, and pipeline design that matters in one place. Write real code against real data. No round you have not rehearsed.
Ready: A readiness score tracks how prepared you are for every topic interviewers ask about. When it is green across the board, you will ace it. No guessing.
Frequently Asked Questions
I write SQL every day and I still bombed a technical screen. What happened?
Production work and interview performance are different skills. You do not fail on knowledge. You fail on structuring an answer under time pressure with unfamiliar tables and someone watching. Every challenge here is timed and live so you build the muscle of producing correct code when it counts.
I have no idea what my target company actually tests. How do I not waste a month?
Every session targets your weakest topic against the pattern mix your target company tests most heavily. You are not working through a generic top-100 list. You are closing the specific gaps that would cost you the offer, so every hour of prep counts.
The data modeling round scares me and I cannot find anywhere to practice it.
That round cuts more senior candidates than any other, and most people just re-read the Kimball book and hope. You get a product scenario, build the schema from scratch, and get evaluated on your grain, dimensions, and SCD strategies before you are doing it live.
I keep telling myself one more week of prep and it has been three months.
That loop never ends on its own. A readiness score per target company shows exactly which rounds you would pass today and which ones would cost you the offer. When you can see the gap closing, you stop guessing and start scheduling.
Every company seems to test something completely different. How do I prep for that?
They do. Databricks leans hard on Spark internals, Meta on SQL windows, Stripe on idempotent pipelines. Your practice set is weighted to your target company's actual pattern distribution, not a one-size-fits-all question bank.