Design a rate limiter for a public API: for example, no more than 100 requests per minute per API key. The service runs on several instances.
~10 min by voice
How to approach it
This checks whether the candidate can design a distributed component: choose an algorithm and understand its trade-offs, move state into a shared store, make updates atomic, and think through behavior on failures and when the limit is exceeded.
The interviewer will ask this question and listen. Think out loud and ask for a hint if you need one. When you're done, pause or tap “That's my answer”. In about a minute, your score and the points you covered show up here.