A Kotlin developer designs and builds applications using Kotlin, a statically-typed programming language that runs on the Java Virtual Machine (JVM). They leverage Kotlin's concise syntax to write code that's easier to read and maintain. Their tasks include creating new software, updating existing applications, and fixing bugs. They often work with Android Studio for mobile app development, as Google officially supports Kotlin for Android. Additionally, they may work with frameworks like Spring for backend development. They also need to test, troubleshoot, and optimize their code to ensure it runs efficiently and reliably. They often collaborate with other developers, designers, and stakeholders.