Http4k is a lightweight HTTP library written in Kotlin that enables serving and consuming of HTTP services in a functional and testable way. Unlike many other libraries and frameworks which have complicated abstractions and workflows, http4k captures the essence of communication over HTTP with few simple concepts. In this session I will explain and demo the core concepts in http4k by live coding from scratch http server for noughts and crosses game. Target audience: Software developers with couple years of experience using a programming language like Java, Kotlin or Scala. Dmitry has been programming since DOS times. He spent the last 15 years or so in Java lands most recently working with server-side Kotlin.