A LoopBack developer designs and implements APIs using LoopBack, a highly extensible, open-source Node.js framework. They create dynamic end-to-end REST APIs with little coding, using the framework's tools to define models and connect them with backend services. They also ensure seamless integration with databases, web services, and other platforms. LoopBack developers may also be responsible for customizing, extending, and securing these APIs, as well as optimizing their performance. They also troubleshoot and fix any issues that arise, ensuring the APIs function as intended and deliver the required services effectively and efficiently.