Cloudflares automatic TTL is 5 minutes. Web browsers will look up your records and try to connect to one of the returned ips, if that one doesn't work it'll use

Cloudflares automatic TTL is 5 minutes. Web browsers will look up your records and try to connect to one of the returned ips, if that one doesn't work it'll use another one. The fact that the client does this for us means we can keep the TTL quite high (5 minutes) without 5 minutes downtime if we lose connectivity to one IP. This is also used to load balance, a single load balancer can't handle a trillion connections, so we round robin DNS for load balancing before the load balancers. There's also anycasting which is something cloudflare uses a lot. Which means you're announcing the same IP block from many locations, and with how BGP works (which is the defacto protocol for exchanging route information on the internet) the "closer" you are the more likely the route is to be chosen (AS path distance). Meaning sites behind Cloudflare is protected by thousands of servers listening to the two same addresses you see if you're behind a Cloudflare protected site and behind these thousands of servers are even more thousands of servers. This means if i were to launch a 10Gbps DoS from my server, it would hit the Cloudflare datacenter closest to me, and there's nothing i can do about it, meaning the rest of the world is unaffected. No, I'm not afiliated with CF. It's just an approachable example, i believe (but don't know) that Fastly has the same featureset (that I've mentioned above)