they don't run backend/databases though?
Everything is a Mainframe or SAP installation under the hood somewhere, but layers and layers of API mean that product teams can mostly ignore the complexity and ship a mediocre app that is only really a frontend.
It's not really something that will run your Rails backend, but it has the potential of doing a lot for creative small teams.
[1] https://vercel.com/docs/concepts/functions/serverless-functi...