I have a site (now at https://steadbytes.netlify.app) that was using a custom domain registered with Amazon. I used Route53 to set up the correct records to allow my domain (steadbytes.com) to be used by netlify for this site. Earlier this week I removed the custom domain from the site and reset the records in Route53 to point to Amazon nameservers/SOA. It’s been well over the 48 hour TTL now (by several days) and the DNS records are still resolving to the Netlify name servers:
$ whois steadbytes.com | grep -i "name server"
Name Server: dns1.p02.nsone.net
Name Server: dns2.p02.nsone.net
Name Server: dns3.p02.nsone.net
Name Server: dns4.p02.nsone.net
Is there something I’m missing or am I just unlucky with TTLs not being observed particularly well? 
@SteadBytes Welcome to the Netlify community.
Although it’s not clear from your description, it seems as though you used to have your DNS with Netlify, but now you’re trying to switch it to Amazon.
I’m not seeing any evidence that Amazon is doing the DNS for your custom domain, so I guess the first question is: What DNS entries did you make with Route53 / Amazon in preparation for the name server transition?
The second question is, have you tried deleting the custom domain from your Netlify dashboard? Doing so might rattle loose the DNS propagation that seems now to be half Netlify and half nothing.
Yes that’s correct - apologies if it was unclear.
I have added the following NS records:
ns-1050.awsdns-03.org
ns-967.awsdns-56.net
ns-1991.awsdns-56.co.uk
ns-51.awsdns-06.com
In addition to an SOA record:
ns-1991.awsdns-56. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
I had already removed the DNS entries from the Netlify dashboard.
@SteadBytes OK, I can see the changes you made, but although you have delegated DNS to AWS you seem not to have any DNS entries there, because you site isn’t loading. You have disconnected from Netlify DNS though.
So, is this what you want … to be running Amazon DNS that points to nothing, and to be disconnected from Netlify DNS?
@gregraven Yes, for now at least. I will be pointing the Amazon DNS to something else and needed control of the DNS for that domain name again. That said, it seems that the DNS has updated now and was likely a caching issue (isn’t it always 
):
whois steadbytes.com | grep -i "name server"
Name Server: ns-1050.awsdns-03.org
Name Server: ns-1991.awsdns-56.co.uk
Name Server: ns-51.awsdns-06.com
Name Server: ns-967.awsdns-56.net
Thank you very much for your help!