Heck, I've done mainframe-to-unix porting. The concerns about "lock-in" raised here are silly and trivial. If you're writing serverless code, it's already stateless and inside a well-defined and well-documented box. The hard stuff, always, is the business logic.

If you feel locked in, you lift-and-shift your serverless logic to a new platform. Write some shims and wrappers. It ain't that goddamn hard.