A Common Lisp developer designs, codes, tests, and debugs software applications using the Common Lisp programming language. They are responsible for creating algorithms, defining data structures, and managing system functionality. They often work on artificial intelligence systems, as Lisp is particularly suited for AI development. The developer also troubleshoots and optimizes code, ensuring performance efficiency. They work in a team environment, collaborating with other software developers and stakeholders. Continuous learning and staying updated with new technologies is also a part of their role. They may also write documentation to describe program development, logic, and coding processes.