A Domino Developer is responsible for designing, developing, and maintaining applications using HCL Domino (formerly IBM Notes/Domino). They create workflows, databases, and integrations to support business processes, often using LotusScript, Java, JavaScript, and @Formula language. Domino Developers also troubleshoot issues, optimize performance, and ensure security within the Domino environment. Their role may involve migrating legacy applications, integrating with other systems, and modernizing existing infrastructures.