At Repl.it our mission is to make programming more accessible, which means our coding environment needs to be lightweight, load fast, and work from anywhere in the world. However, as with so many software projects that evolve with time, we accumulated some bloat (luckily, we haven't included a mail client yet) and quite a few ad-hoc hacks to glue everything together. In this post, we'll go over how we designed our new IDE to have a small core (everything is a plugin), to be easily customizable (even on the fly), and to server-render.