The data returned by whois ip-address
appears to be very useful and more accurate than the data I get from the maxmind geoip databsae I am currently using.
Where does the data come from and are there any rate limits?
Of course I will cache information for an ip, but nevertheless I am expecting tens to hundrets of thousands of calls daily.
Please note that I am quering information on IP addresses, not domain names. Therefore the registrars are not involved. The data appears to come from RIPE and ARIN, however they do not write about any limits in their terms and there is also no information available whether the databases are somehow distributed in a DNS like fashion or come from a single server.