A CoffeeScript developer designs and implements software solutions using CoffeeScript, a programming language that compiles into JavaScript. Their tasks include writing clean, efficient code, troubleshooting and debugging applications, and integrating user-facing elements with server-side logic. They also optimize applications for speed and scalability, and ensure cross-platform compatibility. They collaborate with other team members to define and design new features, and often contribute to the entire web development process, from conception to deployment. Additionally, they maintain and improve existing codebases, and ensure the technical feasibility of UI/UX designs.