A GWT-RPC developer specializes in using Google Web Toolkit (GWT) to create asynchronous, service-oriented applications. The developer uses GWT's Remote Procedure Call (RPC) framework to enable communication between the client and server sides of an application. This involves writing Java code that's compiled to highly optimized JavaScript, defining service interfaces and their asynchronous counterparts, and implementing these interfaces on the server side. The developer also handles serialization and deserialization of objects for transport across the network. Additionally, they troubleshoot and resolve any RPC-related issues, ensuring efficient, responsive web applications.