Targeting sub 1s build times seems like the wrong optimisation. If you write your content in markdown you can just preview it in a browser with ~1ms latency, because you don't need no fancy build system to do that. When you've written your post, put it in the site data structure, hit build, and go make a coffee.

If your objective is to put content on the internet, this will be more than enough. If it is instead to create The Most Perfectest Website Framework Ever, then unfortunately Spring Boot already exists 😏

Go for the fun, but your issue is a non issue. I use Zola (built with Rust) and it is very very fast. A full build of ~200 pages takes ~2s and in dev mode, changes are reflected almost instantly.