What does the VARTA error `idempotency_key_in_progress` mean?

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.