Or we could use something like SQLite which has text indexing capabilities, and is cross platform and can be used to do a bunch of adhoc queries too.
Speed isn't the end all be all here. Accessibility is. If we give answers in 100-200ms, that's more than plenty fast. Even if you're returning in 1-2micros, at the end of the day, a meat bag is still doing the reading. Meat bags are slow.