Kotlin coroutines have revolutionized JVM development, especially on Android and the backend, as they let us easily implement efficient and reliable multithreading. Their cutting-edge design and features are ideally suited to modern use cases. In this book, we will explore how Kotlin coroutines work and how we can use them to improve our code. This is a practical book. It shows everything by examples and focuses on real-life use cases. As this technology is already widely used on Android and backend applications, we will see how we can use it there and what the best practices are. As a developer experienced in both backend and Android, I primarily focus on these two perspectives in this book. These are currently the two major industry applications of Kotlin, and it’s evident that coroutines were largely designed to suit these use cases well1. So, you might say that this book is mainly designed for Android and backend developers, but it should be just as useful for other developers using Kotlin.