Amazon·Machine Learning Engineer·Technical Phone Screen
May 2026
Amazon ML Engineer interview that went deep on bandit algorithms, way deeper than I expected. They weren't satisfied with just naming the algorithms, they pushed hard on tradeoffs, production edge cases, and things like delayed rewards that I hadn't drilled enough.
- What are multi-armed bandit algorithms, and when would you choose one over a traditional A/B test?
- Compare epsilon-greedy, UCB, and Thompson sampling. How do they differ in terms of regret, exploration-exploitation balance, and underlying assumptions?
- How would you extend standard bandit approaches to contextual bandits, and what changes in terms of modeling and complexity?
- How do you handle delayed or batched rewards in a bandit system?
- How do you detect and handle non-stationarity or distribution drift in a deployed bandit?
- How would you do offline policy evaluation for a bandit before deploying it to production?
- What safety mechanisms or guardrails would you put around a bandit system running in production?
“Felt pretty solid here.” The rest of the author's notes on Machine Learning Engineer interview at Amazon, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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