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Jane Street Interview Questions

The questions to prepare for Jane Street interviews, across all roles. Questions from real interview reports rank first. Updated weekly.

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1
CodingStart here. 7 questions · ~66 min
O(1) Insert Delete Random SetEasy
Practice

Implement a set-like structure using an array and hash map to support insert, delete, and random access in average O(1) time.

Hash TablesArraysData StructuresJane Street
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2
Statistics & Probability7 questions · ~66 min
Expected Flips for Two HeadsMedium
Recently asked

Compute the expected waiting time to see two consecutive heads when flipping a fair coin.

DistributionsExpected ValueConditional ProbabilityJane Street
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3
Pipelines5 questions · ~47 min
Data Quality and Schema EvolutionMedium

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

schema evolutionData ModelingQualityJane Street
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4
Strategy6 questions · ~56 min
Estimate Gas Stations in a CityEasy

A market sizing question that tests how you structure assumptions, estimate demand, and sanity check the number of gas stations in a city.

EstimationTAM/SAM/SOMMarket SizingJane Street
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5
SQL & Data Manipulation6 questions + 3 drills · ~86 min
Millisecond-Accurate Trade JoinHard

Tests ability to write efficient SQL for aligning trades to order book state at millisecond granularity.

Joinsfinancial dataperformanceJane Street
Flag Suspicious Lyft Trip CardsMedium
Practice
Practice drill

Use joins, CTEs, aggregations, and CASE logic to flag payment cards with anomalous Lyft trip activity.

Data AnalysisRisk Managementanomaly detectionLyft
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
Resolve Conflicting Customer AttributesMedium
Practice
Practice drill

Use joins, CTEs, and row ranking to resolve conflicting customer profile values across ACME House systems.

JoinsData WranglingQualityRamsey SolutionsACME House
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6
Execution6 questions · ~56 min
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7
More topics13 questions · ~122 min
Diagnose a Metric Drop After LaunchMedium

Investigate why a key KPI moved the wrong way after a product change and separate signal from noise.

Lagging IndicatorsLeading IndicatorsDiagnosisJane Street
Common Pitfalls in Experiment ResultsHard

Identify the main pitfalls that can distort A/B test interpretation and explain how to guard against them.

PeekingNovelty EffectSample Ratio MismatchJane Street
High-Frequency Data Ingestion SystemHard
Recently asked

Assesses system design skills for low-latency, high-throughput ingestion pipelines at scale.

system designdata ingestionJane Street
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The finish line: interview-readyComplete all 50 questions plus 3 hands-on drills to finish this plan.