A Mongoose ORM developer designs, implements, and manages data structures using the Mongoose Object-Relational Mapping (ORM) system for Node.js applications. They create schemas and models for storing data, perform CRUD operations, and handle database relationships. They also implement middleware for pre and post-processing of data. They use Mongoose's validation techniques to ensure data integrity. The developer also optimizes queries for performance, handles asynchronous operations, and troubleshoots any issues related to data handling. They are expected to collaborate with other developers to integrate the database with the application logic.