Assuming they're spread out over ~10-12 hours (some crazy morning people, some crazy nocturnal people), that's only ~4-6 commits per hour. Most problems will b

Assuming they're spread out over ~10-12 hours (some crazy morning people, some crazy nocturnal people), that's only ~4-6 commits per hour. Most problems will be discovered by someone and reported in an hour, and most of those will also be discoverable in a dataset on a system like Scuba - https://www.facebook.com/notes/facebook-engineering/under-the-hood-data-diving-with-scuba/10150599692628920 https://www.facebook.com/notes/facebook-engineering/under-th... - and you can identify the first time that particular issue happened. If you're lucky, it lines up exactly to a commit landing, and you only need to look at that. Otherwise, due to sampling, maybe you need to look at two or three commits before your first report/dataset hit. You can also use some intuition to look at which of the last n commits are the likely cause. A URL generation issue? Probably the commit in the URL generation code. You'd do the same thing with a larger bundled rollout, but over a larger number of commits (50, in the case of a daily push).