How GitHub uses merge queue to ship hundreds of changes every day

GitHub's introduction of the merge queue system has revolutionized the way it manages pull requests, significantly enhancing deployment efficiency and developer satisfaction. Initially developed to address the complexities and inefficiencies of the previous 'trains' system that grouped multiple pull requests for deployment, merge queue dynamically forms and manages groups of pull requests, automates builds, and enforces branch protection rules to prevent updates to failing commits. This system has resulted in a 33% reduction in average wait time for shipping changes and has doubled the volume of pull requests merged into GitHub's large monorepo compared to previous years. The transition to merge queue was carefully phased to ensure continuity and minimize disruption across GitHub's global, remote-first engineering teams. Now generally available, merge queue offers a streamlined, automated approach to managing code changes, reflecting GitHub's commitment to improving the developer experience and maintaining high deployment standards.