One of your servers may be down because of automatic system upgrades. The update takes only the time for a machine to reboot and is quick.
During the downtime, your application should continue to work smoothly. Squarescale detects that the machine goes down and will reschedule services running on that machine elsewhere. Your services will continue to be available.
If the machine contains a service that is configured to be load balanced, the load balancer will detect the service goes down and will redirect request to other spare services and to the new service scheduled to replace the old one that has been stopped.