Idempotency

Every public mutable operation should receive Idempotency-Key. In MuPag it protects you from double clicks, network retries, client timeouts and accidental worker replays.

How to generate it

• Use UUID v4, ULID or a stable business-event hash.
• Reuse the same key only for the same semantic intent.
• If the payload changes, generate a new key.

Where to apply it

• POST /v1/charges
• POST /v1/customers
• POST /v1/products
• POST /v1/products/{productId}/plans
• POST /v1/coupons
• POST /v1/checkout-sessions
• POST /v1/subscriptions

What to persist

Store the key, the canonical payload and your business identifier. That makes 409 Conflict easy to reconcile with the original successful request.