Honestly, I don't see the point in "serverless" as they call it (which is actually servers / centralized clouds), except maybe to have a common compilation target for stuff, to limit the surface area of APIs.

Literally you can just control a lot more about your stack and do what you want (mysql, outside APIs, etc.) and use your servers as origin servers for the CDN. You can take your regular PHP site, separate out the "session-dependent" stuff into a separate service, and the rest is static resources that can be cached.

Or even better: do ACTUAL serverless:

https://qbix.com/blog/2018/04/03/onward-to-qbix-platform-2-0...

https://qbix.com/blog/2020/01/02/the-case-for-building-clien...

I gave a talk recently about it, that you might be interested in: https://www.youtube.com/watch?v=yKPKuH6YCTc