A Database Testing Developer primarily ensures that databases work seamlessly and securely. Their responsibilities include creating tests to validate data integrity, accuracy, and consistency. They also check the system's performance and functionality under different conditions, ensuring it can handle high volumes of data. They run SQL queries to verify stored procedures, triggers, and functions in the database. They also ensure data security by checking encryption and data access permissions. Moreover, they are responsible for identifying, diagnosing, and fixing database-related issues, thus ensuring smooth and efficient data management. They work closely with other developers, system administrators, and project managers.