API Rate Limiter Design
Design a rate-limiting service that protects APIs shared by many users and client applications. Product teams should be able to define limits for different identities and endpoints, and callers should receive a clear decision for every request. The limiter sits on a latency-sensitive path, must handle very high traffic, and should behave predictably when instances or regions disagree or become unavailable. Clarify the policy semantics and failure behavior before walking through your design.
