Centrifugo
Scalable real-time messaging server in a language-agnostic way
... 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. There is also the possibility to proxy WebSocket events to the application backend over HTTP or GRPC and more.