We already kind of do that on our CDN backend, this is just a small part of it. But we never actually needed to do geolocation, instead we just ping the "stable

We already kind of do that on our CDN backend, this is just a small part of it. But we never actually needed to do geolocation, instead we just ping the "stable" pingable IPs we found from all of our locations, save the results into a DB and when a request from that subnet comes to PowerDNS we just select the datacenter with the lowest RTT on the fly. I'll see if it's possible to get the routing/GeoIP information for all IPs as that's something we could use too.