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Updated weekly · Last refresh Aug 30

Unknowns Data Engineer Interview Questions

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

15questions
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1
PipelinesStart here. 11 questions · ~89 min
Data Quality in ETL PipelinesEasy

Approach for maintaining data quality and integrity across ETL pipelines.

IdempotencyData ModelingQualityUnknowns
Explain ETL in Data EngineeringEasy

Explain the ETL process, why it matters, and how it fits into a practical data pipeline.

ETLOrchestrationQualityUnknowns
Batch vs Stream Processing Trade-offsMedium

Compare batch and stream processing across latency, complexity, cost, and data quality in a modern analytics pipeline.

InfrastructureStream ProcessingETLUnknowns
Diagnose an Integration Pipeline IssueMedium

Structured approach to diagnose failures in an ETL integration, from source extraction through orchestration, data quality, and idempotent recovery.

ToolsDependenciesQualityUnknowns
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2
More topics4 questions · ~33 min
Choosing Data Structures at ScaleEasy

Explain which data structures work best for large datasets based on access patterns, memory use, and update costs.

Hash TablesArraysHeapUnknowns
SQL Query for Data ExtractionEasy

Tests your SQL proficiency for retrieving and shaping data for analysis.

JoinsGroup ByAggregationsUnknowns
Optimizing Slow QueriesMedium

Tests your SQL performance tuning approach and ability to diagnose bottlenecks.

Joinsquery optimizationAggregationsUnknowns
Leadership Project ExampleMedium

Tests ownership, execution, and leadership behaviors in delivering project outcomes.

Conflict ResolutionLeadershipteamworkUnknowns

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Hands-on SQL practiceWrite and run real queries in the editor. 3 drills · ~30 min
Second Highest Trader SalaryEasy
Practice
Recently asked
Practice drill

Find the second highest distinct salary from a single table using basic PostgreSQL ordering and limiting.

SubqueriesRankingSortingeClinicalWorksInformaticaSpectraforce Technologies
Monthly Sales Trends by CategoryMedium
Practice
Practice drill

Aggregate monthly sales by product category and use LAG to calculate month-over-month changes.

InfrastructureToolsData WranglingTotal Wine & MoreInc.Benjamin Moore
Contact Center Agent Performance MetricsHard
Practice
Practice drill

Compute daily agent call KPIs and SLA using joins, aggregations, and window ranking in a contact center model.

ETLAggregationsData ModelingADP
The finish line: interview-readyComplete all 15 questions plus 3 hands-on drills to finish this plan.