A MongoLab developer primarily works with MongoDB, a cross-platform document-oriented database program. They are responsible for designing, implementing, and managing databases on MongoLab (now MongoDB Atlas), a Database-as-a-Service (DBaaS) platform. This involves creating schemas, performing CRUD operations, setting up data replication and backup, and ensuring database performance and security. They also integrate MongoDB with various applications and services, troubleshoot issues, and optimize database performance. Their role often requires a deep understanding of NoSQL databases, cloud services, and programming languages like JavaScript and Python. They work closely with other developers to ensure seamless data flow and storage.