idempotency-and-retries

From the author

Make an operation safe to repeat — idempotency keys and their storage, what a replay returns, retry policy with backoff and jitter, and how to reconcile after a timeout whose outcome is unknown. Use when an operation has an external side effect (a charge, an email, a provisioning call), when a caller needs to retry safely, or when duplicates have already appeared in production. Not for webhook receipt mechanics, not for database transaction design, and not for choosing a queue.