The HyperText Transfer Protocol (HTTP) 504 Gateway Timeout server error response code indicates that the server, while acting as a gateway or proxy, did not get a response in time from the upstream server that it needed in order to complete the request.Aug 13, 2021
504 Gateway Timeout – HTTP | MDN – Mozilla
What causes a 504 Gateway Timeout?
A 504 Gateway Timeout error indicates that the web server is waiting too long to respond from another server and “timing out.” There can be many reasons for this timeout: the other server is not functioning properly, overloaded, or down. The other server need not always be external (e.g. CDN, API gateway).