What's the state of server-side Kotlin now, is it usable and what kind of JVM are cloud hosts running it on? Kotlin seems like one of the best languages out there.
We use it in production with spring boot and deploy a single jar file on azure. Works pretty well
We're using Kotlin with Spring at the moment and everyone on the team prefers it over Java. I suggested Kotlin when they laughed at my suggestion of using Clojure. Ah well.
Kotlin is widely used internally at Amazon. In both AWS and retail.
Not only usable, but becoming very widely used. It's no different from Java for deployment.