I've seen a few server-side Swift frameworks (for building web apps or API apps) such as Perfect[1] and Kitura[2] (which is backed by IBM). It's not clear to me how much uptake they have so far.
The API's not stable, the framework is in very active development.
I imagine things will settle down in a year or two - until then, there are so many great alternatives (other languages), that I don't see Swift gaining much ground.