503 / Service Unavailable

“The server is currently unavailable (because it is overloaded or down for maintenance).[2] Generally, this is a temporary state.“ — wikipedia

“The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.
Note: The existence of the 503 status code does not imply that a server must use it when becoming overloaded. Some servers may wish to simply refuse the connection.“ — ietf

503 / code reference(s)
Rails HTTP Status Symbol
:service_unavailable
← return