Ktor

Ktor lets a Kotlin developer write a server as a few lines of routing code and add features (authentication, JSON serialisation, WebSockets, CORS) as plugins only when needed. It is asynchronous throughout thanks to coroutines, and runs on engines such as Netty or its own CIO engine.

The same project provides the Ktor client, a multiplatform HTTP client that Kotlin Multiplatform apps use on Android, iOS, desktop and the web. Compared with Spring Boot it is smaller and more explicit, with fewer built-in integrations.