There is also some interesting work (for dotty only atm) on doing the type checking in two phases which would allow the second phase to be parallelized. This could be paired together with the Rsc type checker for the first pass for even bigger improvements.
According to [1] a working version will be ready before originally planned:
> Recently, Stu Hood came up with a groundbreaking idea. He suggested > that Rsc can become useful much earlier that we initially thought.
[0] https://github.com/twitter/rsc
[1] https://github.com/twitter/rsc/commit/ebc3019c06c9e175311541...