While CI tools can run test on every pull request when it's opened, and on every branch after it's pushed, it may not be sufficient to avoid broken builds. For instance, if you have two pull requests that modify dependent code, the tests could pass on each pull request independently and Github would allow the merge but the build may break after the merge. You may configure Github to block pull request that is not up-to-date with master to avoid this issue. But this may not scale with your team. This configuration means every individual engineer has to: Update current branch with master. Wait for the test to pass again. Merge the pull request when it's done. In case another pull request is merged before that, repeat the steps above.

MergeQueue monitors all pull requests on your Github repository Instead of manually merging pull requests, the engineers label them when ready. MergeQueue prioritizes ready PRs based on FIFO. Based on your configuration, MergeQueue performs some operations on PRs. Merges PR when all the merge criteria has been met. Reports and dequeues pull requests that fail the criteria.