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Prep plan
Updated weekly · Last refresh Aug 30

Hays Data Engineer Interview Questions

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

22questions
~3htotal time
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1
PipelinesStart here. 13 questions · ~105 min
ETL vs ELT Trade-offsEasy

Compare ETL and ELT, and explain when ELT is the better pipeline pattern.

ETLELTData ModelingHays
Data Quality in ETL PipelinesEasy

Approach for maintaining data quality and integrity across ETL pipelines.

IdempotencyData ModelingQualityHays
Handling Missing Data in PipelinesMedium

Approach for handling missing data in an ML data pipeline, including validation, imputation, and safe downstream consumption.

InfrastructureETLBatch ProcessingHays
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2
SQL & Data Manipulation3 questions + 3 drills · ~54 min
Top Routes Query in SQLMedium

Tests ability to translate business metrics into correct SQL queries.

RankingAggregationsHays
Optimizing SQL Query PerformanceMedium

Tests SQL performance tuning skills and practical strategies for faster, cheaper queries.

Window FunctionsJoinsAggregationsHays
Tuning Slow BigQuery CostsHard

Tests advanced BigQuery optimization and cost-performance tradeoff reasoning.

Window FunctionsJoinsAggregationsHays
SQL Average Salary by DepartmentEasy
Practice
Practice drill

Calculate average active salary by Hays department using a LEFT JOIN, GROUP BY, and NULL-safe aggregation.

sql queryAggregationsHaysCATERPILLARTuring
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
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

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3
Behavioral & Leadership5 questions · ~40 min
Cross-Team Collaboration Under PressureEasy

Tests teamwork and collaboration through communication, stakeholder alignment, and ownership in a cross-functional analytical setting.

Conflict ResolutionCommunicationLeadershipHays
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4
More topics1 question · ~8 min
Optimizing Python for Large DatasetsMedium

Tests performance optimization skills for Python data processing workloads.

Hash TablesArraysSortingHays
The finish line: interview-readyComplete all 22 questions plus 3 hands-on drills to finish this plan.