[ithkuil]

if you need DNS based failover you want low TTLs , e.g Google.com A record is 100s

[gibybo]

Still though, aren't most consumers using their ISP's DNS servers, which will cache the same response for all of their customers in a region?

[takeda]

It all depends on how high ttl is, the number of queries increase exponentially as you decrease it, with ttl=0 you have no caching.

My company makes about 160qps which translates to about half billion per month, so it doesn't seem too unrealistic.