I'd guess that, like most platforms, youtube content follows a power law concerning the activities, meaning that 99% of the traffic comes from 1% of the content

I'd guess that, like most platforms, youtube content follows a power law concerning the activities, meaning that 99% of the traffic comes from 1% of the content (or something along those lines). In the Netflix CDN, each node has a fixed library that's restocked at fixed intervals, at least that's what I remember from reading their requirement document for ISPs interested in having a CDN node in their network. The Google CDN is likely more dynamic with nodes having region dependent libraries but nothing that you can't manage.