Recently, Google's John Mueller posted about what to do if your site goes offline. The advice was to serve a 503 server status code if the outage is short term. So someone asked if they can serve a 502 server status code instead. John Mueller said you shouldn't.
John was asked on Twitter "does 502 error work as well or it is required to be 503 only ? I want to check because hosting companies throw different error codes in different cases."
John responded on Twitter "502 is not the same as a 503 -- I'd recommend using the proper result code. These durations aren't documented in absolute terms since they can change & vary." He gave this analogy, "If a bus is temporarily delayed for an unknown time, how long do you wait until you look for something else?"
The HyperText Transfer Protocol (HTTP) 502 Bad Gateway server error response code indicates that the server, while acting as a gateway or proxy, received an invalid response from the upstream server.
So stick with the right server status response code for the right situation.
Forum discussion at Twitter.
