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Duolingo Interview Questions

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

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1
SQL & Data ManipulationStart here. 5 questions + 1 drill · ~61 min
2
Coding5 questions · ~51 min
Longest Substring Without RepeatsMedium
Practice

Find the longest substring with all unique characters using a sliding window.

Hash TablesStringsTwo PointersDuolingo
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3
Metrics5 questions · ~51 min
Using Metrics to Drive DecisionsEasy

Explain how you used a KPI and supporting metrics to diagnose a product issue and make a concrete product decision.

Funnel AnalysisKPIsLeading IndicatorsDuolingo
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4
Execution5 questions · ~51 min
Choose Project Management ToolsEasy

Explain which project management tools you use most effectively and why, including how they support execution and stakeholder alignment.

CommunicationRoadmappingScope ManagementDuolingo
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5
Machine Learning5 questions · ~51 min
Supervised vs Unsupervised LearningEasy

Explain how supervised and unsupervised learning differ, and ground the distinction in a practical ML example.

Unsupervised LearningFeature EngineeringBias-Variance TradeoffDuolingo
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6
Product Sense5 questions · ~51 min
Align Product With User NeedsMedium

A framework for connecting user needs to business goals, then making product decisions with clear trade-offs and measurable outcomes.

User NeedsValue PropositionProduct VisionDuolingo
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7
More topics20 questions · ~204 min
Pitfalls in Streaming Experiment AnalysisHard

Identify major online experiment pitfalls and explain how they can bias results in a streaming product A/B test.

Network InterferenceNovelty EffectSample Ratio MismatchDuolingo
Successful Sales Strategy ExampleEasy

Explain a sales strategy you built and executed, including segmentation, objection handling, and how it drove account growth.

Competitive AnalysisGo-to-MarketGrowth StrategyDuolingo
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The finish line: interview-readyComplete all 50 questions plus 1 hands-on drill to finish this plan.