dedupe_requests

https://github.com/tilo/dedupe_requests

Detects and rejects duplicate inbound POST/PUT/PATCH requests with a 409/conflict, with no client-side idempotency key required. The server auto-computes a fingerprint of each mutating request, claims it atomically in Redis, and short-circuits duplicates seen within a configurable time window, so they don't overwhelm your server or cause 5xx errors.