Top 20
Prep plan
Updated weekly · Last refresh Sep 21

Duolingo Machine Learning Engineer Interview Questions

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

20questions
~3htotal time
Track your progressSign up free to work through all 20 questions and resume where you left off.
Start practicing free →
1
CodingStart here. 3 questions · ~27 min
Implement Gradient DescentEasy
Practice

Implement batch gradient descent to fit a one-feature linear model for Plymouth Rock Assurance claim severity estimates.

MathArraysGradient DescentDuolingo
Optimizing Sorting for Large DatasetsMedium

Explain how to choose and optimize sorting approaches for large datasets based on memory, data distribution, and stability requirements.

ArraysSortingGreedyDuolingo
More Coding questions with a free account
2
Machine Learning6 questions · ~54 min
Hyperparameter Tuning for ML ModelsMedium

Explain a practical process for tuning model hyperparameters using cross-validation and overfitting checks.

Hyperparameter TuningCross-ValidationBias-Variance TradeoffDuolingo
Feature Selection for Supervised ModelsMedium

Explain a practical feature selection process using validation, regularization, and model-based importance to improve generalization.

Cross-ValidationFeature EngineeringRegularizationDuolingo
More Machine Learning questions with a free account
3
System Design3 questions · ~27 min
Design a Personalized Product RecommenderHard

Design an end-to-end product recommendation system for a large e-commerce marketplace with strict latency and freshness needs.

Feature StoreFeature DriftModel ServingDuolingo
Predicting Language ProficiencyHard

Tests end-to-end system thinking for modeling proficiency from interaction signals.

ML RankingFeature StoreRecommendation SystemsDuolingo
More System Design questions with a free account
4
Behavioral & Leadership6 questions · ~54 min
More Behavioral & Leadership questions with a free account
5
More topics2 questions · ~18 min
Evaluate a Recommendation SystemMedium

Evaluate whether a recommendation system is improving engagement and ranking quality, not just offline metrics.

PrecisionAccuracyRecallDuolingo
Designing a Duolingo A/B TestMedium

Tests experimental design, metrics, and decision-making for product changes at Duolingo.

Hypothesis TestingStatistical SignificanceA/B TestingDuolingo

Sign up to see every question

Create a free account to unlock this list and practice real interview questions.

Get my prep plan
The finish line: interview-readyComplete all 20 questions to finish this plan.