Although Kotlin is, from a language perspective, 100% interoperable with Java, due to the slight paradigm shift (nullability) there might be some pain when using Java frameworks, e.g.: the need of private var lateinit when using JUnit, having to use compiler plugins to open up Spring annotated beans or a generated zero-arg constructor for Hibernate. This talk goes through a full fledged alternative to the common Java stack when writing microservices, using: Ktor (Web framework), Kodein (DI container), Exposed (SQL library), Spek (test framework), Gradle Kotlin DSL, ...