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Updated weekly · Last refresh Aug 30

Eightfold Data Engineer Interview Questions

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

16questions
~2htotal time
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1
PipelinesStart here. 12 questions · ~101 min
Design High-Throughput Event PipelineHard

Design a real-time event pipeline that can handle millions of events per second with sub-second latency.

data pipelineevent processinglatencyEightfold
Data Quality and Schema EvolutionMedium

Approach for handling schema changes and data quality checks in a high-volume data lake pipeline.

schema evolutionData ModelingQualityEightfold
Backfill While Preserving Real TimeHard

Approach for running large historical backfills without breaking real-time pipeline freshness or correctness.

Stream ProcessingDependenciesBackfillingEightfold
Production Pipeline Quality MonitoringMedium

Approach for adding data quality checks, observability, and production monitoring to a data pipeline.

Data QualitymonitoringobservabilityEightfold
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2
Coding3 questions · ~25 min
Efficient Large-Scale DeduplicationMedium

Assesses your strategies for removing duplicates at scale while controlling cost and correctness.

deduplicationdata processinglarge datasetsEightfold
Flatten Nested JSON for SQLMedium

Tests your ability to implement data transformations that make semi-structured data queryable.

Data Manipulationsql analysisEightfold
Compute Moving Averages in StreamsMedium

Evaluates your streaming windowing and state management approach for time-series analytics.

data streamsEightfold

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3
More topics1 question · ~8 min
Optimize Slow SQL or SparkMedium

Tests your ability to diagnose and improve performance using profiling, indexing/partitioning, and query rewrites.

Performance TuningEightfold
Hands-on SQL practiceWrite and run real queries in the editor. 3 drills · ~30 min
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
SQL Duplicate Record DetectionEasy
Practice
Practice drill

Find duplicate American Institutes for Research assessment submissions using a CTE, GROUP BY, HAVING, and joins.

deduplicationsqldata integrityAmerican Institutes for ResearchMacy's
SQL Data Quality ChecksHard
Practice
Practice drill

Detect missing fields, duplicate transaction keys, invalid amounts, and merchant reference issues with PostgreSQL CTEs and joins.

Data Qualitynull handlingdata integritySigmoid
The finish line: interview-readyComplete all 16 questions plus 3 hands-on drills to finish this plan.