HTTP 504 Gateway Timeout indicates a gateway or proxy did not receive a timely response from an upstream server. The upstream didn't respond at all within the timeout period — contrast with 502 where the upstream responded but with invalid data. Common causes: upstream server is too slow (increase timeout or optimize), network partition between gateway and upstream, DNS resolution failure for the upstream host, or upstream server's connection pool is exhausted.
Response includes the status code, standard headers (including Content-Type), and a small diagnostic JSON body describing the request and returned status.
Simulator URL (copy in the app after load — not a normal link):
https://httpstatus.com/api/status/504
Example request:
curl -i "https://httpstatus.com/api/status/504"