Kotlin: Write code for cross-platform compatibility
Kotlin is an open source, object-oriented programming language with type inference, which allows developers to be more concise with their syntax.
gRPC--a modern, open source remote procedure call (RPC) framework that can run anywhere--provides better performance, less boilerplate code to manage, and a strongly typed schema for microservices in addition to other benefits. This article demonstrates building a full gRPC-based server and client written in Kotlin. Then it shows how to use Envoy to provide server-side load balancing between multiple instances of the service.
Spring has a new way to code to and it's called Spring Functional or SpringFu. This article uses Kotlin to showcase some of the benefits--such as the ability to write cleaner, more-readable code and gain more flow control--you get from SpringFu.
You can write more-readable code using Kotlin's coroutines feature. in my opinion, coroutines provide a cleaner approach than reactive programming.