A BreezeJS developer designs and implements web applications using BreezeJS, a JavaScript library that manages data in rich client applications. They handle data querying, caching, and synchronization tasks, ensuring smooth data flow between server and client. They work with other technologies like ASP.NET, Node.js, and AngularJS for backend services and frontend interaction respectively. They also debug and fix issues, optimize application performance, and ensure data integrity and security. Their role involves understanding client needs, translating them into technical requirements, and continually updating their skills with evolving BreezeJS features.