I've used in a production android app that was initially java only and we introduced kotlin before the language was 1.0. Language was a bit unstable back then a

I've used in a production android app that was initially java only and we introduced kotlin before the language was 1.0. Language was a bit unstable back then and it was getting updated often but since 1.0 it's been stable. Definitely makes android development more pleasant as you have more tools and language features. It feels like a modern typesafe language. The things I like the most is that you can mix and match the 2 language with little effort and that JetBrains has done an amazing work integrating the language in the IDE (Android Studio) which is based on the IntelliJ platform. Our team was comprised of polyglot devs (java/obj-c/swift) so kotlin felt more like swift in some ways so working both on ios and android made it pleasant and porting was easier. I wouldn't recommend you convert your java project to 100% kotlin to start but the excellent interop (better than obj-c/swift) between java-kotlin makes it easy to try some stuff out and see if you like it. They have a very helpful slack channel where all the kotlin devs and language designers hang out so they are always responsive to questions. The community is still small but very helpful and the folk are nice and inclusive. So to answer you question it is ready for production and tools are excellent as well as the language is very pragmatic and has evolved pre-1.0 based on real life developer feedback not from academics who are not coding every day.