Harness CI has demonstrated a significant reduction in build time for Facebook's Proxygen project, achieving a 7x faster build compared to GitHub Actions, by utilizing efficient parallel execution and optimized cloud infrastructure. Proxygen, a collection of C++ HTTP libraries developed by Facebook, aims to provide a high-performance HTTP framework with sensible defaults, distinct from projects like Apache or nginx. The text outlines the steps to set up Proxygen on Harness CI, detailing the configuration of a pipeline that includes stages for fetching dependencies, building them, constructing Proxygen, copying artifacts, and testing the project. The use of a matrix strategy in the pipeline allows for parallel execution of dependency-related steps, significantly optimizing resource usage and reducing build times. This efficiency is particularly beneficial for managing the growing size and complexity of open-source projects, which can challenge meeting release deadlines and effective testing. Overall, Harness CI showcases how its features and optimizations can enhance developer productivity by shortening build times and potentially reducing costs.