Centrifugo

Centrifugo is language-agnostic. It's a standalone server with a simple API that integrates well with an application written in any programming language. 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. There is also the possibility to proxy WebSocket events to the application backend over HTTP or GRPC and more.