Can you explain the principle of idempotency and its importance in interaction systems?

Idempotence is a property of an operation where multiple executions with the same input produce the same result as if the operation was performed once.

In interaction systems (for example, REST API), this is important for reliability: if a request is repeated due to network failures, the repeated call will not further change the system's state.

Example:

• The HTTP method GET is usually idempotent — a request to retrieve data does not change the state.
• PUT — updating a resource; if performed multiple times with the same data, the result will be the same.
• POST is usually not idempotent, as it can create new resources with each call.

Idempotence helps avoid errors and simplifies handling repeated requests in distributed systems.