> “we don’t store the keys and just rely on the hash to be really good” I think that's fine if you actually use a really good hash (e.g. a 128-bit cryptographi

> “we don’t store the keys and just rely on the hash to be really good” I think that's fine if you actually use a really good hash (e.g. a 128-bit cryptographic PRF). But I wouldn't be comfortable with hashes shorter than that or which aren't crypto quality. People already make such assumptions when assuming uniqueness v4 UUIDs.