Free Dynamic DNS

Thanks for the service. Personally I would lower the TTL to 120 or less.

Dyndns is used for personal stuff. There is no point caching a FQDN almost nobody use. If anything, low TTL is a benefit for recursive resolvers like 1.1.1.1 or ISPs. Those FQDN should not be cached as there is zero benefit keeping them in their cached for one guy hitting it once per day.