reaatech/idempotency-middleware

These packages give you idempotency middleware for POST, PUT, and PATCH requests — duplicate requests with the same `Idempotency-Key` header return the cached original response instead of re-executing side effects. You'd adopt them to safely retry payment charges, webhook deliveries, or any mutation where duplicate execution would cause data corruption or duplicate charges. The core provides a pluggable `StorageAdapter` interface with in-memory, Redis, DynamoDB, and Firestore backends, plus framework adapters for Express, Koa, and a generic handler for Lambda or gRPC, all with built-in distributed locking that prevents concurrent handler execution for the same key.