TL;DR
- idempotency key api retry 2026
- For backend engineers building order, payment, and webhook APIs.
Who this is for
- For backend engineers building order, payment, and webhook APIs.
Keyword (SEO)
idempotency key api retry 2026
The problem
- Clients retry the same POST after timeouts—without a key you can double charge or duplicate orders.
- Mobile networks and proxies increase duplicate risk.
The pattern
- Send Idempotency-Key (UUID) per business operation.
- Store key hash + response snapshot with TTL—replays return the same status/body.
- Align TTL with PSP rules and your own risk window.
Integrations
- Many PSPs support idempotency—map consistently.
- Verify webhook signatures before mutating state.
Common mistakes
- Clients retry the same POST after timeouts—without a key you can double charge or duplicate orders.
- Mobile networks and proxies increase duplicate risk.
FAQ
Should GET be idempotent?
GET should be safe to repeat; keys matter most for POST/PUT with side effects.