The answer is "yes." We had indexes - but it's also a little more complicated than that, as we're storing IPv4 and IPv6 ranges in a single table in a format _designed_ to be indexed a particular way.
In the article, we refer to this as "decimal lexical" formatting, where we're taking the IPs and making them integers but actually treating them as strings. We're doing this in both Redis with sorted sets and then in a single table in SQLite.
I was going to explain all this in the article, but it was too long already, so it will be a future blog post.