If you have a small team of engineers and you need the added productivity of a more ergonomic language, then go ahead with Kotlin. In particular it's good for "

If you have a small team of engineers and you need the added productivity of a more ergonomic language, then go ahead with Kotlin. In particular it's good for "lite-functional" style with OO mixed in, and your engineers get to keep all the familiarity they have with the JVM ecosystem. It's not some panacea though, and at the end of the day Java is the system language of the JVM. New VM features are not built to cater to the guest languages. In the case of virtual threads we have a directly competing "async" solution to Kotlin coroutines. So you may see further ecosystem split between libraries catering to Android and those catering to backend work.