except it's not "here-and-there". everything down from `<html>` is re-SSR'd and fully re-hydrated on each page load.
here-and-there is what jquery does.
I ask because my server app is not a nodejs process and don't want to add one for now but do want to avoid heavy state management and client side routing as you did.
https://krausest.github.io/js-framework-benchmark/current.ht...
but re-hydration is much faster than actually building the dom from scratch in js. instead of 20ms, it might be 60ms + some extra for render/layout time.
however, unless you have very DOM-heavy pages, the perf should still be great from a user's perspective. you may get some flashing between page navigation since when you build the DOM in JS with domvm it's not streamed, but when the browser is parsing server-sent html, it is. the only way to know is to try it for your specific case.
if you need SEO, it's probably sub-optimal and may take longer to for Google & Bing to index, from everything i've read.
I have been doing the latter for some time with https://github.com/airbnb/hypernova for a rails API.