Real-time apps, or evented apps that incorporate push-based interactivity, are the basis for a new generation of in-browser capabilities such as chat, large-scale games, collaborative editing and low-latency notifications. Though there are many technologies supporting the real-time movemement, four stand out in particular: Ruby, Node.js, MongoDB and Socket.IO.

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https://devcenter.heroku.com/articles/realtime-polyglot-app-node-ruby-mongodb-socketio