Redis makes it easy to synchronize state over multiple nodes in the realtime cluster.
Go is great for realtime. The gorilla websocket library is excellent. Also the low memory consumption of a single goroutine means you can easily handle many WS connections on a single node.
We use AWS's ELB for load balancing the nodes in our realtime cluster.
StatsD is used to track the number of messages we're publishing and the type of realtime subscribers. So it shows the number of longpoll connections, the number of websocket connections etc. It also tracks how Redis is performing.