upstream_timeout

The upstream did not answer in time. For a mutating request the outcome is unknown (`metadata.outcome: unknown`): it may have executed.

HTTP 504. Unknown: it may have executed. Resolve it with the same idempotency key before acting.

Likely cause: The terminal or broker is slow.

What to do: Never resend a trade blindly: repeat it with the same Idempotency-Key (or clientId) to learn the real outcome. Reads can be retried.

Retry: Only with the same Idempotency-Key (or clientId). The first attempt may have executed; never resend a trade blindly.

Listed under Outages and timeouts in Errors. Send the error’s requestId to support and we can find the request.