What is the significance of idempotency in a system and why is it needed?

Idempotency is a property of an operation where multiple executions with the same input data do not change the state of the system after the first call.

Why is idempotency needed:

• It allows safe repetition of requests without the risk of unwanted side effects (for example, in case of network failures or retries).
• It simplifies error handling and retries in distributed systems.
• It ensures predictability and stability of API and service behavior.

Example: The HTTP method PUT is usually idempotent — sending several identical requests to update a resource will have the same result, unlike POST, which can create new resources with each call.