A Google Guava developer designs and implements robust, scalable, and efficient software applications using the Google Guava libraries in Java. They use Guava's utilities for collections, caching, primitives support, concurrency, common annotations, string processing, I/O, and more. They write clean, maintainable code and ensure it's efficiently tested, debugged, and documented. They also identify and fix potential software issues, optimize existing functionalities, and keep up-to-date with the latest industry trends. Their role involves collaborating with other team members to deliver high-quality software solutions that meet specific user requirements.