A Ganglia developer works with Ganglia, an open-source, scalable, and distributed system designed to monitor computer systems and networks. They develop, implement, and maintain the Ganglia software, ensuring efficient performance monitoring and data collection. Their tasks involve creating visualizations to represent data, diagnosing issues, and optimizing system performance. They also work on improving the software's scalability and reliability, and often collaborate with other developers to integrate Ganglia with other systems. Additionally, they may contribute to the open-source community by sharing code, bug fixes, and improvements.