Backend
Designing Idempotent APIs for Reliability
Idempotency keys and deterministic state transitions prevent costly duplicate writes.
Why idempotency matters
Retries are normal in distributed systems. Without idempotency, a transient timeout can create duplicate charges, orders, or provisioning operations.
Implementation pattern
- Require client-generated idempotency key for mutating endpoints.
- Store request hash and final response per key.
- Return the original success payload for repeated requests.
Operational checks
- Alert on duplicate key conflicts with mismatched payloads.
- Track retry volume by endpoint.
- Enforce key TTL and cleanup policies.