All the Java frameworks are usable in Kotlin. I don't know any specific that covers all the bases Rails does - what I usually see are patchworks and a lot of Sp

All the Java frameworks are usable in Kotlin. I don't know any specific that covers all the bases Rails does - what I usually see are patchworks and a lot of SpringCore/JPA/Hibernate. Personally, my go-to choice is always something simpler (eg Netty, Vertx, Spark etc - those are more like Express.js or Sinatra than Rails). There's also JavaLite, which explicitly tries to look like Rails (including database migrations, an ActiveRecord-style ORM, etc)