504 Gateway Timeout
A proxy, load balancer or CDN waited for the application to answer and gave up after its timeout. The application is up but hanging or far too slow.
Where it failed: a proxy or load balancer
What visitors see
A "504 Gateway Timeout" page after a long wait, usually 30 to 100 seconds.
Usual causes
- A slow database query or a locked table.
- A call to another service (a payment API, a search server) that hangs.
- Too few workers, so requests wait in a queue past the proxy's timeout.
- A long task (an export, an import) run inside a web request.
How to tell which one it is
- 504 means the proxy reached the application and waited; 502 means it got a bad or no answer at once.
- The slow-query log or the application's tracing shows what the request was waiting on.
What to do
- Find the slow query or call (slow-query log, APM traces) and fix or cache it.
- Move long tasks to a background job and answer the request at once.
- Raise the timeout only as a stopgap (nginx proxy_read_timeout, the load balancer's idle timeout); it hides the problem.
Check the site now
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