A MogileFS Developer designs, implements, and maintains MogileFS, an open-source distributed file system. They work on the server-side backend coding, using Perl and MySQL, to ensure data is stored across multiple networked servers, providing redundancy and fault-tolerance. Their tasks include optimizing system performance, debugging issues, and developing new features. They also collaborate with other team members to design system architecture and interfaces, ensuring the system is scalable and reliable. Moreover, they are responsible for creating system documentation and updating existing ones. They also need to stay updated with the latest industry trends and technologies.