How do you enforce token buckets in a distributed system?
Use Redis or Memcached to store per-client token state (tokens_available, last_refill_time). Each API gateway queries and updates this state atomically. Return `429 Too Many Requests` with a `Retry-After` header when the bucket is empty. Distribute tokens across gateways by keeping the refill rate low enough that skew is acceptable.
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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