Idempotency
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What is Idempotency?
The property that repeating the same intended operation has the same effect as doing it once.
For checkout, the same request twice must produce the same result: one payment, no double charge. Send a unique idempotency key for that payment and reuse it on retries. The server remembers the operation and prevents duplicate effects; it may return the saved response. A new purchase needs a new key, and provider retention limits matter.
When you would use it
Use it when payments, queued tasks, or incoming notifications may be repeated.
Common operations
- Reuse one operation key across retries.
- Remember processed operation identifiers to prevent duplicate effects.