> ## Documentation Index
> Fetch the complete documentation index at: https://developers.safarapi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Idempotency

> Safe retries on write requests with Idempotency-Key

Every write (`POST`, `PUT`, `PATCH`, `DELETE`) requires an `Idempotency-Key`
header — in **both** production and sandbox. It makes retries safe: a network
timeout on `POST /bookings` can be retried without double-booking.

```
Idempotency-Key: 3f1c6b90-8e2a-4d77-b5c4-9a0e1f2d3c4b
```

* **UUID v4**, unique per logical operation (one per booking attempt, not one per process).
* Retained **24 hours**. After that the key is forgotten and a reuse is treated as a new operation.

## Semantics

| Situation                | Result                                                     |
| ------------------------ | ---------------------------------------------------------- |
| Same key, same body      | The original response is replayed. No second operation.    |
| Same key, different body | `409` `idempotency.key.conflict`. **No action performed.** |
| New key                  | Processed normally.                                        |

<Warning>
  Generate the key **before** the first attempt and reuse the *same* key for every
  retry of that operation. Generating a fresh key per retry defeats the protection.
</Warning>

## Recommended retry pattern

1. Mint one `Idempotency-Key` for the operation.
2. Send the request. On `2xx`/`4xx` (except `429`), you have a definitive answer — stop.
3. On timeout, `5xx`, or `429`, retry **with the same key** after a backoff.
4. A replayed success returns the original body — safe to treat as success.

Idempotency is independent from [request signing](/introduction/authentication):
sandbox `sk_test_*` keys skip the signature but still require `Idempotency-Key`.