Run WHOIS at scale and store the results into a DB. gTLD operators are required to provide WHOIS services, and WHOIS tells you whether any given domain is regi

Run WHOIS at scale and store the results into a DB. gTLD operators are required to provide WHOIS services, and WHOIS tells you whether any given domain is registered or not. There are companies that will happily sell you this data in a more usable format.