A ChefDK (Chef Development Kit) developer is responsible for coding, testing, and managing infrastructure applications. They use Chef, a powerful automation platform that transforms complex infrastructure into code, to bring machines and software to the desired state. ChefDK provides a set of tools for developing and testing Chef cookbooks. The developer uses these tools to automate processes, manage system configurations, and ensure the efficient deployment of applications. They work closely with system admins and other IT staff to ensure the seamless operation of all systems. They also troubleshoot any issues related to the infrastructure's software and hardware.