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?
I’ve never really understood the whole TTL thing. Will the domain essentially point to nothing if the TTL runs out while the DNS server is down or will it default to older record?
The record will expire and, in this scenario, effectively become non-existent.
Once upon a time TTLs we’re rather long so temporary outages were less impactive. These days TTLs of less than a minute are common to accommodate redundancy. It doesn’t do want good to have redundant systems if DNS keep pointing at the downed system during an outage.
It will most likely point to nothing. DNS servers can have performance improvements of sending the stale data while fetching it from the main source in order to be quicker, even though this is technically not correct. But in many cases the associated IP will not have changed anyway.