I’d encourage JSS over CSSinJS. Having a .css output file is no good for modularity, eg why send ALL THE STYLES when you just need the styles for the landing page? react-dom-stream is neat, but I’ll honestly never render so much html to make it worthwhile, and for small html payloads, it’s actually a net loss in speed. The exception would be something like a CMS with a ton of static content, in which case you’d be rockin!