I'd like to see a fully distributed version. All you need is 4B hosts (IPV6 FTW) named N.domain.com (where N varies from 0 to 4B-1). The driver app sends N to the first host (0.domain.com). Each host compares the incoming N with their N.domain.com name; if they match, return the host's true/false value. If they don't match, forward the request to (N+1).domain.com and return the result.
Also, I think this can easily be implemented; you don’t need 4B hosts, just 4B DNS entries, and those, you can create with a single wildcard entry (https://en.wikipedia.org/wiki/Wildcard_DNS_record)
