A Flask-SQLAlchemy developer designs and implements web applications using the Flask framework and SQLAlchemy toolkit in Python. They create dynamic web applications, manage server-side logic, and implement data storage solutions, ensuring data consistency and integrity. They use SQLAlchemy for database abstraction, allowing interaction with various databases like PostgreSQL, MySQL, and SQLite. They also handle migrations, updates, and querying of data. Furthermore, they maintain code quality, troubleshoot, and fix bugs to optimize web application performance. Additionally, they may work with front-end developers to integrate user-facing elements and ensure the application meets user needs.