Uber's journey to optimize their monorepo CI/CD process involved overcoming the challenges of managing a large codebase with over 50 million lines of code and 3,000 engineers. Initially, Uber's adoption of a Go monorepo enhanced build efficiency, but the increasing scale demanded further innovations. They transitioned from Make and go build to using Bazel, which allowed for better dependency management and CI optimization, preventing the need to validate the entire monorepo for small changes. To further enhance build times and workflow efficiency, Uber developed SubmitQueue, a system designed to keep the main branch stable while handling high volumes of commits. However, large changes continued to pose bottlenecks. Uber’s team implemented strategies such as dynamic builds with parallel job execution, containerization, and cache optimization to reduce build times. They eventually replaced Jenkins with Buildkite for its dynamic scalability and flexibility, which significantly improved developer productivity and the overall CI process. These improvements included better job orchestration, enhanced build visibility, automated dependency management, and a more developer-friendly interface, ultimately enhancing the developer experience and maintaining a fast, reliable CI/CD process.