HTTP 504 — Gateway Timeout
5xx Server Error
What it means
A proxy did not get a response from the upstream server in time.
What to do about it
The backend is too slow. Profile the slow endpoint, add a database index, or raise the proxy timeout — but a timeout is a symptom, and raising it usually just moves the problem.
Where it sits
504 belongs to the 5xx family: The server failed to fulfil an apparently valid request. The fix is on the server side.
HTTP/1.1 504 Gateway TimeoutChecking it yourself
# see the status code and headers only
curl -sI https://example.com/path
# follow redirects and print each hop
curl -sIL -o /dev/null -w "%{http_code} %{url_effective}\n" https://example.com/path
# JavaScript
const r = await fetch(url);
console.log(r.status, r.statusText);