Cloud9 is entirely built on Node.js and can be used to debug and develop other Node.js applications. This fun recursive fact we used to very quickly use the tool we built to refine and develop the tool we are building. The opensource version of Cloud9 can be pulled from Github and the app is served from a single Node.js process. Built on Socket.IO and Connect for the server, Cloud9 has a full WebDAV implementation in Node.js, and can start other Node.js processes and connect to its debugport to control the application. In this talk, Rik will go through the overall architecture of Cloud9, touching on many design choices made for writing the system in Node.js, dealing with Asynchronous code, and what scaling characteristics that came up.