That’s actually an awesome question, we love when people are interested in computing and technology! As you can imagine, Cloud9 is a quite complex app. I’ll try to share some of the key aspects:
Infrastructure: Workspaces are hosted on a custom system based on Docker. We put a lot of work into building and optimizing this system are very proud of how well it scales and how fast new Cloud9 workspaces are provisioned. It’s coded in Node.js and lots of Bash. The code is closed source and not available to the public.
Hosting is done using Google Cloud Platform and we are distributed over several global datacenter locations. This helps to minimize the latency between server and client. Google handles the computing, network, and storage for us.