How Facebook pushes updates to the site
It's interesting that their entire release architecture seems to be focused on never pushing bad things out to production, whereas given their traffic they could probably push things out much sooner (minutes after they're committed) to small parts of their overall traffic, and slowly increase the traffic on those pieces of code as they prove themselves to be stable, or quickly revert them if they're not.That would mean having a lot of versions of Facebook live at any one point, but as those parts prove themselves stable they'd gradually be rolled out to all of their traffic.One point that also wasn't covered is that as they're pushing things out they'll only cherry-pick parts of their codebase depending on which engineers they have around. I wonder if they have a lot of hairy merge conflicts around release time due to that, and bugs in production resulting purely from those merge conflicts. Or worse, subtle bugs resulting in change A going out, but being programmed against a function that was changed in change B, which is not going out because the author of change B isn't in today.