domain name availability checks using EPP and not WHOIS (CentralNic)
Use of the Whois for perfoming domain name availability checks is STRONGLY DISCOURAGED. CentralNic does not guarantee, and registrars should not assume, the accuracy or timeliness of the data produced by the Whois system. Furthermore, CentralNic may change the layout or content of WHOIS records at any time, which may break automated parsers of WHOIS responses.
Furthermore, in order to ensure the stability of the service in the face of abusive activity, we may impose temporary rate limits and minimum round-trip times without notice.
Registrars wishing to do high volume domain name availability checks are STRONGLY ADVISED to use EPP, which offers significant benefits over the Whois service.
My server IP is often running into problems with CentralNic due to manny whois lookups for domain availability. It has now come to an argument on whether or not we should continue to provide these domain extensions.
I know WHMCS uses the WHOIS servers to determine the state of a domain name, but I do not think this is the best way to do this. ( as you can see above ).