Design Patterns · Junior · Question 71 of 75

What does it mean that an operation is idempotent?

✓Correct answer: Repeating it gives the same result as doing it once (e.g. setting a value, deleting by id)
2It runs only once
3It has no side effects at all

Explanation

Idempotent operations are safe to retry after timeouts. "Add 1" isn't idempotent; "set to 5" is.

Further reading

Wikipedia: Idempotence ↗

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