Sure, that works too. The upside of just storing a random string is you don't ever need to deal with secret management, key rotation, ciphers getting broken, et

Sure, that works too. The upside of just storing a random string is you don't ever need to deal with secret management, key rotation, ciphers getting broken, etc — the random string truly has nothing to do with the real underlying ID, so there's just less work involved in hiding it. The downside is some extra bytes and index space.