In API design, what does idempotence mean and why is it important for MIPC?

• A. Idempotence guarantees faster performance.
• B. Idempotence means an operation cannot be retried.
• C. Idempotence only applies to GET requests.
• D. An operation is idempotent if repeated calls yield the same result as a single call.

Answer: (D)

Idempotence in API design means that issuing the same operation multiple times has the same effect as issuing it once. This matters for MIPC because networks can fail, time out, or be redirected, so clients and intermediaries often retry requests. If the operation is idempotent, those retries won’t change the outcome or create duplicates, keeping the system’s state consistent.

For example, updating a resource with a PUT or deleting a resource with a DELETE should be designed so repeating the same request yields the same final state as the initial request. If you set a user’s profile field with PUT, sending that same request again should not change anything beyond the original update. If you delete a resource, repeating the delete should not recreate something or cause additional side effects.

Idempotence does not promise faster performance, nor does it mean a request can never be retried. It also isn’t limited to GET requests; while GET is typically idempotent, other methods can be designed to be idempotent as well.