Building Idempotent Rails APIs for Webhooks and Payments
1 min read
Partners and processors will deliver the same webhook twice. Your API has to stay safe when they do.
Here’s how we think about idempotency keys, storing fingerprints, and returning consistent responses on replay—without turning controllers into spaghetti.
What you'll learn
- Where to persist keys (Redis vs DB) and for how long
- Separating notifications from money-moving side effects
- Tests that simulate duplicate delivery
Next steps
Align engineering language with finance: at-least-once delivery plus idempotent handlers.