A Mnesia developer designs, builds, and maintains applications using the Mnesia database management system. This involves creating efficient and reliable data models, writing complex database queries, and implementing robust data handling procedures. They also troubleshoot and debug Mnesia-related issues, optimize performance, and ensure data integrity, availability, and security. They may also integrate Mnesia with other systems and technologies, like Erlang programming language. Additionally, they document their work and may collaborate with other developers, sharing their expertise to ensure efficient use of the Mnesia system. They stay updated with the latest advancements in Mnesia and related technologies.