Interview Readiness Platform
Become interview-ready for
data engineering roles.
Write answers to real interview questions, get AI-scored rubric feedback, and track your improvement across topics. Built specifically for Data Engineers.
How it works
Three steps from zero to interview-confident.
What you practice
Core skill areas that come up in every data engineering interview.
20 real DE interview questions
Click any question to sign up and see AI-scored rubric feedback on your answer.
You have a Spark job that runs fine on 10M rows but OOMs on 500M rows. Walk me through how you'd diagnose and fix it.
Explain the difference between SortMergeJoin and BroadcastHashJoin in Spark. When would you force one over the other?
Your dbt model takes 45 minutes to run. How do you find the bottleneck and fix it?
Design an incremental ingestion pipeline for a source table that has no updated_at column.
What's the difference between a fact table and a dimension table? Give a concrete example for an e-commerce company.
Explain SCD Type 2. Write the SQL MERGE statement to implement it.
You're seeing duplicate rows in your gold-layer table. Walk through the steps to identify the root cause.
What is a data contract? Who owns it, and what happens when a producer breaks it?
Compare Kafka delivery semantics: at-most-once vs at-least-once vs exactly-once. When does each matter?
Your Airflow DAG has been running for 6 hours and is stuck. What do you check first?
Explain watermarks in Flink/Spark Streaming. What happens to late-arriving events?
Write a SQL query to find the second-highest salary in each department without using LIMIT or TOP.
What is partition pruning and how does Iceberg's hidden partitioning improve on Hive-style partitioning?
You need to backfill 18 months of data. How do you do it safely without impacting production?
Explain the Medallion Architecture. What goes in Bronze, Silver, and Gold layers?
What's the difference between RANK(), DENSE_RANK(), and ROW_NUMBER()? Give an example where they produce different results.
Your Kafka consumer lag is growing. What are the possible causes and how do you fix each?
Explain Change Data Capture. What are the trade-offs between log-based CDC and query-based CDC?
How does Spark's Adaptive Query Execution (AQE) work? What problems does it solve?
Design a data quality test suite for a payments pipeline. What tests are blocking vs. warning?
Simulate the real interview
Pick a level (mid / senior / staff), go through timed rounds across topics, and get a full report with hiring verdict at the end.
Example DE rounds: Data Modelling → SQL → Python → System Design
Interview guides
Deep dives on what interviewers actually test.
How Interviewers Actually Evaluate Your SQL Answers (It's Not About Correctness)
Most candidates think SQL interviews are pass/fail: either the query works or it doesn't. Senior interviewers are scoring something else entirely. Here's what they're actually writing down.
How to Answer Data Pipeline Reliability Questions in DE Interviews
Incident response, retry strategies, and idempotency design — the reliability topics that senior DE interviewers probe hardest, and how to structure answers that land.
SQL Window Functions: What DE Interviewers Actually Ask
Beyond ROW_NUMBER and RANK — the window function patterns that separate senior DE candidates from mid-level ones. With real interview questions and model answers.
Built for data roles
100+ topics across Data Engineering, Data Science, and Data Analytics. Questions tagged by difficulty, topic, and subtopic — so you always know what you're working on.
Ready to level up?
Join for free. No credit card required. Start with 10 AI-scored practice sessions.