The below image is the recommended approach for managing large volumes of traffic coming through your instances. End-user HTTP traffic can be routed through a load balancer, that can then be handed out to the Distributed Front End Servers. If the front end server cannot directly service the request, it will make a request to the backend load balancer to handle. The URL the front end server will proxy to is based on the Agent External URL configured on System Settings page.
A front end server will not participate in agent communication, workflows, emails, notification services, or cleanup. When connected to a front end server you can still do everything that you would be able to do on a normal UrbanCode Deploy server. Requests for services that are not available on a front end server will proxy a request to the backend.
For more information, see Setting up clusters of servers.