An ASP.NET Core MVC developer designs, develops, and modifies software applications using Microsoft's ASP.NET Core and MVC frameworks. They write server-side web application logic, align application design with business goals, and develop and implement databases. They also ensure the applications are secure and efficient. They utilize MVC's separation of concerns principle to make the code easier to manage and test. They work closely with front-end developers and participate in debugging and UI design. Regular maintenance and updates of the application, as well as troubleshooting and improving existing systems, are also part of their responsibilities.