A MongoDB developer designs, implements, and manages databases using MongoDB, a popular NoSQL database. They work on backend development tasks like creating scripts for data manipulation, ensuring data security, and optimizing database performance. They also create data models, write complex queries, and integrate MongoDB with other services. They collaborate with other team members to understand data requirements and develop solutions. Additionally, they troubleshoot and resolve database issues. Their role requires them to stay updated with the latest MongoDB features and functionalities. They contribute to the overall project by providing efficient, scalable, and maintainable database solutions.