# What does the VARTA error `idempotency_key_in_progress` mean?

A request carrying this `Idempotency-Key` is still being processed.


**HTTP status:** `409`  ·  **Type:** `invalid_request_error`

## What it means

A request carrying this `Idempotency-Key` is still being processed.

## What causes it

The idempotency layer claims the key before the handler runs; a second request with the same key while the first is still in flight raises this (`backend/app/api/v1/idempotency.py`).

## What to do

Wait for the first request to finish and retry with the same key. Don't fire concurrent requests carrying one key.