This is a custom DNS server which allows setting and retrieving text-based data. New values can be written as subdomains and retrieved via a normal TXT lookup.

To set a key: dig @ns.sslip.io put.my-value.my-key.k-v.io txt +short
To get a key: dig @ns.sslip.io my-key.k-v.io txt +short
To delete a key: dig @ns.sslip.io delete.my-key.k-v.io txt +short

k-v.io: DNS-based Key-Value Store