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Updated weekly · Last refresh Sep 22

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
SQL and Python Data WorkMedium
Practice
Practice drill

Use a CTE, join, and conditional aggregation to summarize valid monthly user activity.

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