Java · Senior · Coding

Write a thread-safe RateLimiter class: the constructor takes how many requests per second are allowed, and the tryAcquire method, without waiting, returns true if the request can be let through and false if the limit is exhausted. It will be called concurrently from many threads.

~15 min by voice

How to approach it

The interviewer wants to see whether you can choose a rate-limiting algorithm and explain its trade-off. Second, whether you can make refilling, checking and consuming atomic, so that a race doesn't let an extra request through. Third, whether you avoid the typical traps with time: a non-monotonic clock, losing fractional tokens, unbounded accumulation.

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concurrency rate limiting

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Answer by voice

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.

Best with headphones · ~15 min