Functions aren't necessarily always used in these kind of overarching structures. React frameworks like next.js use them to simply provide backend endpoints for data and logic. I think that's what they're going for, as an addition to their app platform more than anything else

Given the max execution time of 5s and the max memory of 1GB, it seems like that is exactly what this is. Some endpoints to fetch e.g. data off the database or some processing tasks for a frontend framework, like the functions Vercel or Netlify offer.

Nothing to build serious architectures with.