What is the time complexity of token bucket rate limiting?
Token bucket is O(1) time per request and O(1) space per client. The key is lazy refill: compute available tokens only when a request arrives, using elapsed time since the last refill. No background timer thread is needed; no timestamp log is stored per request.
Answered in
Token Buckets: Bounding Rate Limits at the EdgeFixed-window counters leak at boundaries. Token buckets refill steadily, absorb bursts, and bound the sustained rate strictly—the algorithm Stripe uses.
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