503 Service Unavailable
The server is temporarily unable to handle the request, because of overload or maintenance. A Retry-After header may say when to come back.
5xx · Server error
Typical causes
Overload, deploys in progress, a service draining for shutdown, or planned maintenance.
On Bex
A hibernating free-tier Bex service answers its first request with a 503 from the activator (Retry-After: 5) while it wakes; maintenance mode also answers 503.
Defined in RFC 9110, §15.6.4