A Bookshelf.js developer designs, develops, and maintains database applications using the Bookshelf.js library. They incorporate object-relational mapping (ORM) to interface with SQL databases like PostgreSQL, MySQL, and . Their responsibilities include creating data models, managing relationships between data, handling transactions, and ensuring data integrity. They also use Bookshelf.js's features such as eager and lazy loading, transactions, and connection pooling to optimize data retrieval and manipulation. Additionally, they collaborate with other developers, ensuring the database layer integrates seamlessly with front-end and other back-end components, and troubleshoot any issues that may arise.