“Flexible Feature Control at Instagram” article describes how Instagram controls the release of new features to groups of users.
I’ve implemented a very simple feature control mechanism before, but nothing to the sounds of this one. Rolling out to groups of users, conditional control, geo-tagging, and more. On top of it, non-technical users seem to be able to use for tuning the groups. This sounds quite impressive, especially when you think of the Instagram’s user base (400,000,000+ users).