Duolingo Mobile Engineer Interview Questions

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

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CodingStart here. 9 questions · ~83 min

Implement a randomized set with O(1) insert, delete, and uniform random lookup using an array and hash map.

Reverse a String ComplexityEasy

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Reverse a string using two pointers and discuss the O(n) time and space complexity.

RecursionCodingArrays

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System Design6 questions · ~56 min

Assesses data integrity and conflict resolution in offline-first workflows.

Real-Time Event Logging on MobileHard

Assesses logging design balancing observability with battery and data usage.

battery consumption

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Software Architecture4 questions · ~37 min

Optimize Across Devices and ScreensMedium

Tests performance optimization across device tiers and responsive UI considerations for a global audience.

OwnershipDealing With AmbiguityPrioritization

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MVVM vs VIPER for ScalingMedium

Evaluates understanding of mobile architecture choices and how they scale in Duolingo's app.

mobile developmentscalabilitymvvm

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Technical Fundamentals3 questions · ~28 min

Memory Management in Swift/AndroidMedium

Assesses techniques to prevent memory leaks and manage resources in mobile apps.

memory managementandroidswift

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Behavioral & Leadership17 questions · ~158 min

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