Which statement accurately defines idempotence in HTTP requests?

Which statement accurately defines idempotence in HTTP requests?

• A. The property where repeated identical requests leave the server in the same final state.
• B. Only GET is idempotent.
• C. POST is always idempotent.
• D. PATCH is never idempotent.

Answer: (A)

The main idea being tested is idempotence in HTTP requests: repeated identical requests should have the same effect as a single one, leaving the server in the same final state. This matters because network retries can happen, and idempotent operations allow safe retries without producing extra changes. This definition fits well because many HTTP methods are designed so that repeating the same request doesn’t create additional side effects after the first application. For example, requesting a resource twice yields the same data, updating a resource to a specific value keeps it at that value if repeated, and deleting a resource removes it and subsequent identical delete requests don’t change anything further. The other statements don’t capture the idea as accurately. It’s not true that only the GET method is idempotent—PUT and DELETE are also inherently idempotent in their intended semantics. Saying POST is always idempotent is incorrect, since POST typically creates new resources or triggers actions, leading to different results on repeated requests. Likewise, PATCH is not universally non-idempotent; it can be designed to be idempotent if applying the same patch repeatedly yields no further changes.

The main idea being tested is idempotence in HTTP requests: repeated identical requests should have the same effect as a single one, leaving the server in the same final state. This matters because network retries can happen, and idempotent operations allow safe retries without producing extra changes.

This definition fits well because many HTTP methods are designed so that repeating the same request doesn’t create additional side effects after the first application. For example, requesting a resource twice yields the same data, updating a resource to a specific value keeps it at that value if repeated, and deleting a resource removes it and subsequent identical delete requests don’t change anything further.

The other statements don’t capture the idea as accurately. It’s not true that only the GET method is idempotent—PUT and DELETE are also inherently idempotent in their intended semantics. Saying POST is always idempotent is incorrect, since POST typically creates new resources or triggers actions, leading to different results on repeated requests. Likewise, PATCH is not universally non-idempotent; it can be designed to be idempotent if applying the same patch repeatedly yields no further changes.