We had some BIG surprises with Netlify billing. Basically we use the functions they provide, and we racked up a HUGE ass bill. They charge PER request, meaning as soon as we deployed a semi "real time" interface for one app, the usage spiked.

Really, "serverless" is just a fad, and overloaded term. How about you deploy containers instead, and MAYBE have your database provided by a "Saas" provider (database maintenance, backups, upgrades etc, are the real time consumer, not the app server itself)