Most of the Kotlin hype is around Android, but I’m curious about server-side usage. We use Spring Boot for our microservices. Does Kotlin offer significant advantages for backend dev beyond just being "less verbose"? How is the support for libraries like Hibernate and the overall startup performance of the JVM?
3 answers
Kotlin is incredibly powerful for Spring Boot. Spring has first-class support for Kotlin, including dedicated extensions. The biggest advantage is the combination of Coroutines and Spring WebFlux for non-blocking I/O. It allows you to write asynchronous code that looks like synchronous code, which is much easier to maintain than complex Reactor chains. Hibernate works well, though you have to be mindful of "open" classes. Startup time is similar to Java, but the developer productivity boost from features like data classes, default arguments, and extension functions is massive.
Have you looked into the memory footprint differences? In a containerized environment (Docker/K8s), does the Kotlin runtime add any significant overhead compared to a pure Java jar?
We switched to Kotlin for all new microservices two years ago. The reduction in boilerplate (no more Lombok!) made our code reviews much faster and more focused on logic.
Totally agree with Kevin. Removing Lombok and using native Kotlin features makes the project structure so much cleaner. It feels like a modernized Java.
Nancy, in our tests, the memory footprint is virtually identical because Kotlin compiles down to standard JVM bytecode. The only "extra" is the Kotlin standard library, which is only a few megabytes. In fact, by using more efficient data structures and fewer boilerplate objects, we’ve actually seen slightly better memory management in some of our more complex data-processing microservices.