To handle the real-time event syncing we created https://github.com/feathersjs/feathers-sync. It uses a central Redis DB or a MongoDB tailable collection to to synchronize service events between different application instances. Another option is to use your websocket libraries' clustering library, for Socket.io for example there is https://github.com/socketio/socket.io-redis.

This is a very good question. We're definitely planning on adding a section about performance and scaling to the documentation very soon.