Bill Guo worked on the pytorch/executorch repository, delivering a build system optimization focused on architecture-specific model exports. He implemented conditional inclusion of source files in the build configuration, enabling Buck optimization level 3 for internal model exports. Using C++ and build system configuration skills, Bill streamlined the export process by tailoring builds to targeted architectures, which reduced build surface area and improved reliability. His work addressed the need for efficient, architecture-aware builds and laid the foundation for future optimizations. The changes enhanced the internal export workflow, aligning with broader performance and scalability goals while demonstrating depth in software optimization.