Youtube has ~500 hours of video uploaded every minute. Netflix only has content from the past few months/years, and probably only a few thousand hours _total_.

Most of that content will hardly get any views though. Caching the top 10.000 on a daily basis will avoid most traffic.

I guess the reasoning is that Youtube has a way larger catalog while Netflix's catalog is comparatively small. I don't really think this really a legitimate reason though, given that most social media has huge power laws, that is it's likely that 99% of each day's views are for a very tiny number of videos comparable to the size of Netflix's catalog.

Yes, for the remaining 1% youtube has to provide some central service, but that's just a small fraction of their traffic, and if they run into cost problems there they just increase the size of the caches at the ISPs, or introduce layered caching (one for each continent, then one for each ISP, etc). They probably do all of that already.

Storing those huge amount of videos that get maybe 1 view per decade each, that's a different challenge, but I wouldn't say the traffic is. But I don't know youtube's data maybe there is no power law in effect for them, idk.

They do. The key phrase is “highly leverage.”