I suspect parent meant the way the list is processed and how the structure resides in memory. We'd optimally want, e.g., aaa.ai to resolve as fast as zzz.zx. I

I suspect parent meant the way the list is processed and how the structure resides in memory. We'd optimally want, e.g., aaa.ai to resolve as fast as zzz.zx. If we just loaded the file for every query and ran down the list linearly we'd probably see a large disparity with the former being much quicker than the latter. So, the question would be: how is it done in an efficient way? Is it loaded into a btree, is each domain broken into various parts, are certain domains prioritized, threading, compression? Plus, there's the queries for dns updates, and how the results get integrated.