Idempotency
Idempotency means repeating an operation has the same intended effect.
What it is
Idempotency means repeating an operation has the same intended effect.
When to use it
Allow safe retries of payments or creation requests.
Syntax
POST /transfers
Idempotency-Key: 9cc64f1a-unique-client-keyExample
// Persist a unique (actor_id, key) plus request fingerprint and result.
// Same key + same fingerprint: return saved result.
// Same key + different payload: 409 conflict.
// Atomically persist the operation and result in one database transaction.Common mistakes
An in-memory check races; a key without payload comparison can replay the wrong result; define expiry.