An explanation of my magically shrinking build size with subsequent alpha builds

I am a new web dev and I would love an explanation or resources explaining my magically shrinking build folder size with subsequent alpha releases of create-react-app. I have spent a lot of time and energy making my current client-side React as fast as possible through HTTP/2 push, dynamic imports, webP images, optimizing critical rendering paths, just to name a few and for the most part with some success. My app’s LightHouse score went from the 70’s to the high 80’s but, now with the latest alpha I’m making me rethink my optimizations due to my LightHouse scores tanking.

next.66cc7a90: vs next.3e165448:

From 1.1.4 to 66cc7a90 I found most of my savings came from smaller source maps but, 3e165448 is some next level stuff.

React-scripts version	build folder size
1.1.4	12.6 megs.
2.0.0-next.66cc7a90	8.3 megs.
2.0.0-next.3e165448	4.6 megs.

[audiolion]

This has already been covered but I just want to state that I am observing the exact same issue as #4631 where before code splitting on routes would break up my vendor chunks into ~300kb pieces, with 2.0 my vendor is huge and my app code is ~30kb. Code splitting reduces my app code to ~10kb chunks and increases my already big vendor chunk by ~20kb, so it is actually hurting performance.

I think the vendor splitting can be useful but there needs to be some way to split out vendor chunks or perhaps keep the 1.x behavior.

[Timer]

Excellent @wildpow, thank you! I hope to have some free time soon to get to the bottom of this. If anyone can look at is sooner, please do!