• When you say 36 byte GUID, I'm assuming you are talking about a string represented with dashes and without brasses. GUIDs are really 16 bytes, but can be represented as 32 byte strings also. Now if you take that into account, going to a 8 byte bigint (2 ^ 64 = 18,446,744,073,709,551,616 combinations) you are still statistically more likely to have collisions than with GUIDs (2 ^ 128), but for your sample, relatively safe. 🙂

    Robert