The link to the docs https://beta-rxjsdocs.firebaseapp.com can't be accessed.

If it helps, at least the manual page is accessible http://reactivex.io/rxjs/manual/index.html
Still happening, let's wait for a generous sponsor or an unlimited free-plan from Google :D
It's taken care of.
Not sure if the quota has been updated and there's just a delay before the site is served again, but I'm still seeing this too.
_Edit:_ it's just this site https://beta-rxjsdocs.firebaseapp.com/ that has a quota issue
https://rxjs-dev.firebaseapp.com/ is also working.
Most helpful comment
If it helps, at least the manual page is accessible http://reactivex.io/rxjs/manual/index.html