I have firewall update scripts running which continuously poll my DDNS A records for changes. I have the TTL set to the minimum 60 seconds. I use one of the Dynu nameservers, with the aim of getting any changed as soon as possible.

eg.

dig A host.domain.com @ns1.dynu.com +short

However, there seems to be a delay before any change is seem (testing by making changes using the Dynu mobile app). Is there a faster way?

Also, for DNS in general, does an authoritative DNS server not use the TTL value? I assume this is the case as it would not make any sense to me otherwise.