[toast0]

If you disable caching on your recursive resolver, I guess that works...

But I think there is a real issue if caching recursive resolvers don't revalidate delegations. If .com tells you the example.com nameserver is ns1.example.com with some TTL, and ns1.example.com tells you its the nameserver for example.com every time you ask for www.example.com, you should still check in with the .com nameservers ever TTL to validate.

I'm not surprised the default behavior doesn't do that, because when I migrated a high profile domain to new nameservers, we still saw requests to the old servers for more than a month... but it's still ugh, recursive DNS should do better!

[account42]

The point is that that TTL is appropriate for regular lookups but not necessarily for an uptime monitor which has different requirements and tradeoffs to consider.