I work for a startup that uses swift as a server language. The original idea was that both ios and the server would use the same object model which made life easier. Sadly that didn't scale as they started the android app.

We're migrating away from it slowly as we make more microservices but it's been an interesting experience.

It was my first time using swift as I am a server engineer and not an ios engineer.

Its definitely lacking in tooling and libs but it's a really nice language with a good type system (it's not great though but it's easy). It definitely has potential to be a really good server language. I'd be more comfortable using go or python but it's more fun using swift