a request xxx Failed to fetch HTTP status: 504 followed by Database seems to be overloaded

Immediately after an upgrade or installation, error messages a request xxx Failed to fetch HTTP status: 504 and Database seems to be overloaded might be shown after a successful login. This is because of index database maintenance. Please wait some time and then try to login to IP Fabric again. If it takes longer then an hour, don't hesitate to contact our support team.