Explain the concept of idempotence in RESTful APIs with examples.

• A. An idempotent operation yields a different result with each invocation.
• B. An idempotent operation yields the same result regardless of how many times it's invoked (for example GET or PUT).
• C. Idempotence requires that all operations be safe to retry without any impact.
• D. Idempotence applies only to write operations and never to reads.

Answer: (B)

In REST, idempotence means that making the same request multiple times produces the same effect as making it once. So repeated calls don’t stack changes; you end up in the same server state after the first call as you would after any number of identical calls. A GET request is a clear example: fetching the same resource over and over returns the same data and doesn’t alter anything on the server. A PUT request that sets a resource to a specific representation is also idempotent: sending the same payload again yields the same final state as the first time. By contrast, a POST often creates new resources, so repeating it can lead to multiple creations. DELETE is idempotent as well: after the first delete, the resource is gone, and subsequent deletes don’t change that outcome. This is why the best description is that an idempotent operation yields the same result regardless of how many times it’s invoked, with GET and PUT highlighted as typical examples.