Backend & systems·Concurrency and coordination
you can safely run the same operation five times and the system ends up in exactly the state it would after one.
Idempotent
The property that applying an operation repeatedly has the same effect as applying it once. It is what makes retries safe, and retries are unavoidable in any networked system, because a timeout does not tell you whether the work happened. Idempotence is about the effect on state, not about the return value or the work performed.