What Is an Idempotency Token?

An idempotency token, also called an idempotency key, is a unique identifier a client sends with a request so the server can recognize retries of the same operation. The server records the token with the result and returns that stored result if the token arrives again. This makes retrying safe even when the original response was lost.

Why it matters

Networks drop responses, so clients retry; without a token, a retried payment or order can be processed twice. An idempotency token turns at-least-once delivery into an effectively exactly-once outcome.

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