The load balancer must run in "sticky sessions" mode. That means that all subsequent requests belonging to the same session will be send to the same server that handled the first request. The load balancer must be configured accordingly.

In a secured environment it is recommended to tunnel the UM communication via websockets through the load balancer. The load balancer must be configured accordingly.

In the fail-over mode, only one server handles client requests and the second server just runs in background. If the first server fails, the second one takes over all traffic and handles the requests until the main server is available again. In this mode, the two servers have to be more or less identical installations with both, embedded UM and RTBS servers running and both connected to the same database. UM and RTBS configuration is as it would be in a single server scenario, but all client-side UM traffic (websockets) has to be tunneled through the load balancer, also following the fail-over routes.