It’s mostly just CPU. Back when I was designing AcoustID, I really wanted it to be super fast. For Picard-style lookups, even the 2 minutes was too much, but I though it’s a nice compromise.
I didn’t realize AcoustIDs would get used for other purposes, like checking which recordings are the same, it was only meant as a search tool. I’d like to upgrade the database to full fingerprints, but the server code currently doesn’t handle that, so I need to first make it possible to replace those short fingerprints with full ones. It will eventually happen, but it will take time.