idempotency

You prevent duplicate API mutations by enforcing an Idempotency-Key header on critical requests and caching the initial response. Subsequent retries using the same idempotency key return the cached result without reprocessing the mutation.

An idempotency key is a unique client-generated identifier sent in the Idempotency-Key header. The backend checks a durable key store for existing requests, returning cached responses for duplicates while executing only the first mutation.

You need idempotency for critical, non-repeatable API operations like payments, order creation, and inventory adjustments. It guarantees safe retries by preventing network timeouts or double-clicks from executing the same mutation twice.

Yes, implementing idempotency requires a durable key store to track active and completed requests. This persistent storage enables the backend to check for existing keys and cache both successful responses and errors for duplicate requests.

The best way to handle idempotency for payments and orders is requiring a client-generated Idempotency-Key header. The API processes the first request, stores the response, and returns the cached result for subsequent duplicate requests.