FWIW, most of what happens with the unique subdomains is done with the intention of automatically routing you to the nearest edge/pop that has the best chance o

FWIW, most of what happens with the unique subdomains is done with the intention of automatically routing you to the nearest edge/pop that has the best chance of either having the asset cached, or in the best location for routing your request to a datacenter that can serve the asset from disk. By generating the seemingly random subdomains when serving the metadata to the client, it can most efficiently fetch the media to be displayed. It's entirely possible (likely?) that multiple users in the same ISP/location to be vended the same subdomain/url, but physically/topologically distant users will get different urls.