How can idempotency be ensured for address creation API calls?

How can idempotency be ensured for address creation API calls?

• A. Use idempotency-key from client; if same, return existing resource
• B. Rerun the request and create a new resource
• C. Always use POST without idempotency
• D. Use unique response code only

Answer: (A)

Idempotent address creation is achieved by using a client-supplied idempotency key. When the server receives a request with this key, it stores the outcome (the created address) and associates it with that key. If the same key is sent again, the server returns the previously created resource instead of creating a new one. This lets clients safely retry after timeouts or transient errors without risking duplicate addresses, ensuring at-most-once semantics for the operation. Why this works well: the idempotency key uniquely identifies a single operation. Even if network issues cause a retry, the server can detect the duplicate and avoid duplicating resources. It also sets clear expectations: if the first attempt succeeded, the same key will yield the same address; if the first attempt failed, returning the prior successful result prevents partial duplicates. The alternative approaches don’t guarantee safety. Rerunning and creating a new resource can lead to duplicates if the previous submission actually succeeded. Relying on POST without any idempotency mechanism leaves retries ambiguous and can create multiple addresses. Merely using a unique response code doesn’t prevent duplicates or address the retry problem.

Idempotent address creation is achieved by using a client-supplied idempotency key. When the server receives a request with this key, it stores the outcome (the created address) and associates it with that key. If the same key is sent again, the server returns the previously created resource instead of creating a new one. This lets clients safely retry after timeouts or transient errors without risking duplicate addresses, ensuring at-most-once semantics for the operation.

Why this works well: the idempotency key uniquely identifies a single operation. Even if network issues cause a retry, the server can detect the duplicate and avoid duplicating resources. It also sets clear expectations: if the first attempt succeeded, the same key will yield the same address; if the first attempt failed, returning the prior successful result prevents partial duplicates.

The alternative approaches don’t guarantee safety. Rerunning and creating a new resource can lead to duplicates if the previous submission actually succeeded. Relying on POST without any idempotency mechanism leaves retries ambiguous and can create multiple addresses. Merely using a unique response code doesn’t prevent duplicates or address the retry problem.