Can you explain the concept of idempotency in the context of web APIs and why it is important?

Idempotence in web APIs means that calling the same request with the same parameters multiple times will not change the server's state after the first call. For example, if you send a request to update a user's profile, repeated requests with the same data should not create duplicates or alter data additionally.

This is important for reliability: if a request is interrupted or the client does not receive a response, it can retry the request without risking data corruption or unwanted effects. In HTTP, methods GET, PUT, DELETE are considered idempotent, while POST is not.

Example: calling PUT /user/123 with an updated email will always result in the same outcome, regardless of the number of repeats.