What does idempotency mean in MDC3 APIs?

• A. Idempotency means API calls are always authenticated.
• B. Idempotency means repeated calls create a new resource.
• C. Idempotency means APIs are read-only.
• D. Idempotency ensures repeated calls have the same effect as a single call; important for safe API operations in MDC3.

Answer: (D)

Idempotency means that sending the same API request multiple times yields the same result as sending it once. In MDC3 APIs, this matters because networks can be unreliable, so clients may retry requests. If an operation is idempotent, those retries won't cause extra side effects or change the state beyond the initial effect.

Think of it this way: after one successful call, repeating the same call should leave the system in the same state as if you had done it once. For example, retrying a delete should still result in the resource being removed, and retrying a read should not change anything. Some create operations can be designed to be idempotent as well, often using mechanisms like idempotency keys to prevent duplicates on repeated requests.

Other interpretations, like authentication or simply being read-only, don’t capture the core idea. Idempotency is about the effect of repeated requests, not about who is making them or whether reads are involved. The essential takeaway is that repeated calls have the same effect as a single call.