Letting 10 people type in the same file without chaos

CodeSyncAI started as a simple question I couldn't let go of: what happens when ten people type in the same file at the same time? The honest answer, if you're naive about it, is chaos — cursors fighting, text overwriting, edits vanishing. So I built a real-time collaborative IDE to actually solve it. The heart is a WebSocket sync layer backed by MongoDB. Every keystroke becomes an update that gets merged in a conflict-free way, so two people editing the same line don't clobber each other — both changes survive, in a consistent order everyone agrees on. I stress-tested it with 10+ concurrent users hammering the same document and got zero data loss. Then I added the fun part: run the code right in the browser. A Node.js child-process runner behind Express executes it in isolation and streams back the result in under half a second. On top I lazy-loaded the React modules and kept state in Redux, which bumped the Lighthouse score about 35% — because a collaborative editor that loads slowly kills the vibe before anyone even types. Biggest lesson: "real-time" is easy to fake and hard to get right. The magic isn't the WebSocket — it's deciding, deterministically, what the document looks like when everyone edits at once.