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

# idempotency_key_in_use

> A request with the same Idempotency-Key is still running

| | |
| - | - |
| **HTTP status** | `409 Conflict` |
| **Error code** | `idempotency_key_in_use` |
| **Resolve action** | None; wait for `Retry-After` |

## What happened

A retry arrived while the first request sent with the same `Idempotency-Key` was still running, typically because the client timed out sooner than the server finished. The retry did not run, so the write still happens at most once.

## How to fix

Wait `Retry-After` seconds and retry with the same key. Once the first request finishes, a retry gets its response back with `Idempotent-Replayed: true`, or runs again if the first request failed. See [Idempotent requests](/idempotency).


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