If you register a domain with Cloudflare or Route 53, and that service goes down, do your records stay active in the DNS servers? What if the DNS servers go down, I know a lot of people use 8.8.8.8, so if Google’s server goes down, then DNS fails?
What are the potential point of failures for having your own domain?
If the TTL runs out and is unable to reach an authoritative NS, it will yield an error saying that it cannot resolve the domain. If the library catalog is down, you know the book you want is there, you just don’t know the location.
I didn’t intend to imply that you can deal directly with the TLD. You could, theoretically, but they typically don’t have the organization to dream with individual registrants. That’s the job of registrars, who interface through their own software that does calls to the TLD’s APIs.