The entire thing is a JavaFX app (i.e. desktop app), streaming DOM diffs to the browser to render its UI. Every click is processed server side (scrolling is client side). Yet it's actually one of the faster websites out there, at least for me. It looks and feels like a really fast and modern website, and the only time you know it's not the same thing is if you go offline or have bad connectivity.
If you have enough knowledge to efficiently use your database, like by using pipelining and stored procedures with DB enforced security, you can even let users run the whole GUI locally if they want to, and just have it do the underlying queries over the internet. So you get the best of both worlds.
There was a discussion yesterday on HN about the DOM and how it'd be possible to do better, but the blog post didn't propose anything concrete beyond simplifying and splitting layout out from styling in CSS. The nice thing about JavaFX is it's basically that post-DOM vision. You get a "DOM" of scene graph nodes that correspond to real UI elements you care about instead of a pile of divs, it's reactive in the Vue sense (you can bind any attribute to a lazily computed reactive expression or collection), it has CSS but a simplified version that fixes a lot of the problems with web CSS and so on and so forth.
