What was used as the idempotency key?

The idempotency key is a unique identifier used to determine whether a specific operation has already been performed and to prevent its re-execution.

In the context of Embedded / IoT, the idempotency key often uses:

• A unique message or command identifier (e.g., UUID or sequential number).
• A combination of parameters that unambiguously define the operation (e.g., device ID + command number).

Example: if a device receives a command with a unique ID, it stores this ID and, upon receiving the same command again with the same ID, simply ignores it without re-executing the action.