Google's 8.8.8.8: https://developers.google.com/speed/public-dns/cache
Cloudflare's 1.1.1.1: https://1.1.1.1/purge-cache/
The URL above is the documentation of the feature, which happens to also embed it.
Invalidating the cache at one doesn't invalidate the cache downstream of them if they already looked the record up recently. But it does mean that anyone who hadn't looked up the record will get the correct result straight away.
2) What if we purge 1.1.1.1 at 1.1.1.1 ?
3) What if we purge both about the other at the same time?
4) What if we purge aaaaaaa!
So much time...so many ideas...are they sure they will end up well?
And it's not like they need to hold on to any state to work. If you had access you could purge everything and have them start fresh from the root servers, and it would work fine. (As long as the load spike doesn't make it decide to do something dumb, of course.)
8.8.8.8 isn't a DNS name, it's an IP address. There's nothing to purge.
dns.google from dns.google
one.one.one.one from one.one.one.one
dns.google and one.one.one.one