[nsp]

I'm not a node guy, but I found this module for Whois checks - https://npmjs.org/package/whois-available It uses the IANA Whois service, an admittedly cursory look doesn't turn up anything re: rate limits, but you could just do a get request on the root url and only check Whois if it 404s to be safe. http://www.iana.org/whois

[jlogsdon]

Whois wouldn't help here. The problem is that so many requests are going to twitter.com/[username] that they start sending false 404s (or some other error, not 200) because of rate limiting.

[nsp]

I meant to fix the false positives on the domain name availability, or is that issue related somehow?