This is likely fine for the typical "Digital Transformation" projects at huge enterprises that have a ton of cash to spend on things like this.

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.

They do have Edge Functions, which is similar to Lambda. Same with Netlify and Cloudflare. For DBs you have to seek somewhere else.

It's not really something that will run your Rails backend, but it has the potential of doing a lot for creative small teams.

To clarify, we have Serverless Functions[1] which are similar to Lambda, as well as Edge Functions[2] which are similar to Cloudflare Workers.

[1] https://vercel.com/docs/concepts/functions/serverless-functi...

[2] https://vercel.com/edge

Where are your edge locations - doesn’t seem to be any information on your site…

why would any sane person vendor-lock-in all backend code to a single provider?

You don't. You write your backend code and vercel (and others) turn it into serverless functions that can be deployed on AWS or Cloudflare. Or whoever else decides to offer serverless functions. Or you extract your backend and host it yourself. You're not vendor locking yourself.

Haven't yet used their /api serveless functions but I guess it's standard nodejs functions, so not that much vendor lockin

You can deploy next.js application on any server which supports Node.js.

AFAIK they're working on it