Error messages: "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 service desk.