What it means
A property and its mechanisms
HTTP defines idempotency for particular method semantics. A payment API can also provide a request-key mechanism for supported operations. An idempotency key identifies an intended operation under that API’s contract; the key itself is not a synonym for the property.
Recover uncertain operations
Preserve the operation identity before sending a request and follow the provider’s rules for retries, parameter matching and result lookup. A lost response may follow a successful remote action. Reusing a key after its supported retention period or switching providers changes the assumptions and requires a documented recovery decision.
Related concepts
Application programming interface, REST API, Refund, Payment reconciliation.
In practice
A concrete example
After a refund request times out, the client follows that provider’s lookup and retry contract using the original operation identity.
Technical notes & boundaries
Retention, stored responses and failure behavior vary by provider. Idempotency is not a universal guarantee of exactly-once execution or identical response bytes.
Go to the source.
Original references used for this definition. Product details and standards can change.