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CodeSignal Data Engineer Interview Questions

The questions to prepare for a CodeSignal Data Engineer interview. Questions from real interview reports rank first. Updated daily.

4questions
~1htotal time
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1
CodingStart here. 1 question · ~9 min
Explain Solution Time ComplexityEasy
Recently asked

Explain how to analyze an algorithm’s time and space complexity and justify the result from the code structure.

Hash TablesSearchingSortingCodeSignal
2
SQL & Data Manipulation1 question + 3 drills · ~39 min
Optimizing Slow Queries at ScaleHard
Recently asked

Explain how to diagnose and optimize a slow PostgreSQL query on large Apidel Technologies datasets.

SubqueriesJoinsData WranglingCodeSignal
Rolling 30-Day Retention QueryHard
Practice
Practice drill

Calculate acquisition-cohort retention within 30 days by channel using CTEs, joins, and conditional date ranges.

sql queryEvenUpPlayStationAffirm
Top Customers by Net SalesMedium
Practice
Practice drill

Compute top 10 customers by net sales using joins and aggregations, ordering by revenue with deterministic tie-breaking.

SubqueriesJoinsData WranglingGain DigitalTCSZest AI
Left Join vs Inner JoinEasy
Practice
Practice drill

Return all Clipboard users and their matching workspace records, showing how unmatched rows differ between join types.

SubqueriesJoinsData WranglingMilwaukee ToolTiger AnalyticsClipboard

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3
Pipelines2 questions · ~17 min
Data Quality in ETL PipelinesEasy
Recently asked

Approach for maintaining data quality and integrity across ETL pipelines.

IdempotencyData ModelingQualityCodeSignal
Real-Time Event DeduplicationMedium
Recently asked

Evaluates your streaming deduplication strategy for correctness and performance under high throughput.

deduplicationdata streamsCodeSignal
The finish line: interview-readyComplete all 4 questions plus 3 hands-on drills to finish this plan.