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Updated weekly · Last refresh Nov 6

Ookla Data Engineer Interview Questions

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

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1
PipelinesStart here. 3 questions · ~28 min
Debugging Production Data PipelinesMedium

A structured approach to debugging production data pipelines, with focus on orchestration, data quality, idempotency, and safe backfills.

InfrastructureToolsQualityOokla
Data Quality and Schema EvolutionMedium

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

schema evolutionData ModelingQualityOokla
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2
More topics9 questions · ~85 min
Transform Nested JSON to TablesHard
Practice

Flatten nested JSON objects into dotted-path columns and expand arrays of objects into tabular rows.

Data ManipulationpythonOokla
Optimizing SQL Query PerformanceEasy

Explain how to improve SQL query performance using indexing, filtering, and execution plan analysis.

JoinsData WranglingAggregationsOokla
Ingesting High-Frequency Streaming DataHard

Evaluates streaming architecture design, scalability, and throughput considerations.

system designdata ingestionOokla
Choosing Data StructuresMedium

Assesses understanding of data structures and their impact on processing efficiency.

data processingperformanceData StructuresOokla
SQL and Data StructuresMedium

Assesses practical SQL skills and how you model and manipulate data using appropriate data structures.

Data StructuressqlOokla
Python Live CodingMedium

Evaluates Python problem-solving approach, correctness, and ability to work under live coding constraints.

pythonOokla
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Hands-on SQL practiceWrite and run real queries in the editor. 3 drills · ~30 min
SQL Query OptimizationMedium
Practice
Practice drill

Optimize a slow PostgreSQL query that aggregates completed transactions while preserving customers with no matching activity.

Performance Tuningdatabase optimizationindexesDDroisysCapgeminiNomura
Python List and Dictionary BasicsMedium
Practice
Practice drill

Use PostgreSQL aggregations to produce list-like arrays and dictionary-like JSON objects from data records.

Data ManipulationData WranglingData StructuresExl
SQL and Python Coding MixMedium
Practice
Practice drill

Answer two SQL data-manipulation questions and one Python question using the supplied users, posts, and comments data.

JoinsData ManipulationsqlReddit
The finish line: interview-readyComplete all 12 questions plus 3 hands-on drills to finish this plan.