Developed a new Recommendation Engine API and framework for the jd-opensource/xllm repository, focusing on backend extensibility and asynchronous processing. The work involved designing protocol buffers, implementing service layers in C++, and introducing utility functions to support recommendation workflows. By creating the RecCompletionServiceImpl, asynchronous completion requests were efficiently managed, enabling downstream components to fetch and process recommendations through the extended API surface. This approach emphasized modularity and future scalability, leveraging skills in API development, backend architecture, and protobuf schema design. The delivery enhanced the system’s recommendation capabilities, providing a robust foundation for further feature growth within the platform.