180 million isn't all that many. Keeping the answers in a database is trivial. Extracting the answers by trial and error is feasible. You'll probably want a

180 million isn't all that many. Keeping the answers in a database is trivial. Extracting the answers by trial and error is feasible. You'll probably want a large botnet to avoid getting blocked for suspiciously high traffic. If the servers can take an extra kqps or so, you should be done in about a week.