For thirteen years, every DDP message your Meteor app sent rode the same rails: SockJS. Server-side, that's a copy-fork of SockJS v0.3.4 (vintage 2012), carried forward release after release because it worked, and because the transport was tightly integrated with the rest of the DDP stack. It was load-bearing duct tape: fast enough, compatible everywhere, and completely unswappable.
Meteor 3.5 cuts that weld. The DDP WebSocket transport is now pluggable, SockJS is just one implementation behind a small registry, and you can opt into a C/C++ WebSocket server (uWebSockets.js) with a single env var. SockJS stays the default; nothing changes unless you ask.
This post covers four things:
What's new in the transport layer
How to turn on uws in about five minutes
