please see; Add another webserver zammad for load balancing
As far as i understand there are currently no guides or plans to create a HA setup. of course you could make the stateless containers HA, and possibly create a multi-master/master-slave postgres/mysql instance. One thing that could be improved on tho is the startup time of the none-HA containers, and adding health checks in the standard containers to let them fail instead of linger, which sometimes seem to happen. The startup time reduction would help in the uptime, since it could sometime take quite some time to wait for the flag file, and build the caches.