There are some things you can do to protect yourself against these kinds of problem. About 92% of DNS resolvers honour the TTL setting for the NS records from the leaf-node child-zones (e.g. the NS records you control as the owner of a domain). If your domain is reasonably popular, then that caching can help you outlast a problem with your TLDs name-servers. 2 days is a pretty common number for a cache lifetime.<p>Unfortunately for the 8% of resolvers that honour the TTL in the parent domain, you have less control. In this case for .io, the parent-zone NS ttls are just one hour;<p><pre><code> ;; AUTHORITY SECTION:
nic.io. 3600 IN NS ns1.communitydns.net.
nic.io. 3600 IN NS b.nic.ac.
nic.io. 3600 IN NS a.nic.io.
nic.io. 3600 IN NS b.nic.sh.
nic.io. 3600 IN NS ns4.nic.io.
nic.io. 3600 IN NS dns01.cdns.net.
nic.io. 3600 IN NS b.nic.io.
</code></pre>
which I think is relatively short by TLD standards.<p>Another important thing to consider is that the TLD you choose for your domain itself isn't the only TLD that your domain resolution may depend upon. Resolution also depends on all of the domains of your nameservers resolving too. Route 53 assigns every hosted zone 4 nameservers from 4 different TLDs, e.g.;<p><pre><code> example.info. 172800 IN NS ns-1834.awsdns-37.co.uk.
example.info. 172800 IN NS ns-22.awsdns-02.com.
example.info. 172800 IN NS ns-912.awsdns-50.net.
example.info. 172800 IN NS ns-1233.awsdns-26.org.
</code></pre>
So that if any one of those TLDs has a problem it does not cause a resolution failure for your zone. Some other providers do this too, and it's also something you could set up yourself.<p>Full-disclosure: Route 53 engineer here.