“if you just kept everything serialized and merged them one at a time so as not to break your uh main branch you would take a really long time up to days so 20 days in this case to make sure that everything was green.”

At Uber, thousands of daily changes to one monorepo with long builds made one-at-a-time merging impossible, while letting everything merge kept main red. Uber’s SubmitQueue tested likely combinations of pending changes in parallel and kicked out the ones predicted to break trunk. Quoted from YouTube’s auto-generated captions.