Centrifugo
Scalable real-time messaging server in a language-agnostic way
...No need to change an existing application architecture to introduce real-time features. Just add Centrifugo nearby and let it deal with persistent connections. Centrifugo is built in Go language with some smart optimizations inside. It has good performance – see a description of a test stand with one million WebSocket connections and 30 million delivered messages per minute with hardware comparable to one modern server machine. Many built-in features can help to build an attractive real-time application in a limited time. Centrifugo provides different types of subscriptions, hot channel history, instant presence, RPC calls. ...