I've noticed a lot when using CDNs (streaming videos, files, etc) you download from a terrible-looking random-looking URL that looks something like vl-in-f95.1e100.net or a184-26-136-74.deploy.static.akamaitechnologies.com.
YouTube uses ones like https://r8---sn-5hne6ner.googlevideo.com/videoplayback
The thing is: what's the point of these and why are they used? How do DNS records propagate so quickly when generated?