I want to introduce you to a DNS service that has a simple API that's as cheap as chips. This service has two types of accounts: a free account and a paid account.
The free account allows you to have three domains and 15 DNS records for all the domains. However, the administration can disable the API without notice.
On the other hand, the paid account only costs $11 per year but unlocks 160 domains and 600 DNS records with the API being available on an ongoing basis.
Regardless of the type of account, you'll still be able to get your domain, add subdomains to the system's domains, and edit/create various types of records such as A, MX, SOA, NS, SRV, CNAME, HINFO, NAPTR, TXT, SSHFP, LOC, RP, SPF, and WKS.
If you're interested in registering for this service, visit http://ddns.uno/?a=reg. Once registered, you can log in at http://ddns.uno. For technical support, contact support@ddns.uno.
It's worth noting that this service has been free for more than a year, hence, all the infrastructure details were honed during this time. As for abuse cases, fastflux is not tolerated, and the account will be immediately blocked without warning with no chance for refunds. For other burdens, each case will be individually solved, most likely by eliminating the cause of the complaint or editing the problematic record/domain.