An asynchronous developer designs and implements software applications that execute tasks independently of the main application thread. They use programming languages and frameworks that support asynchronous programming to create systems that don't have to wait for some tasks to complete before moving onto others. This can improve the efficiency and performance of applications, especially those dealing with high volumes of input/output operations or heavy network usage. Their work includes handling callbacks, promises, or futures, and managing event-driven programming. They also handle potential issues like race conditions and ensure the smooth running of tasks in a non-blocking manner.