Comment by ivalm 6 days ago
You can assign multiarm bandit trials on a lazy per user basis.
So first time user touches feature A they are assigned to some trial arm T_A and then all subsequent interactions keep them in that trial arm until the trial finishes.
careful when doing that though! i've seen some big eyes when people assumed IDs to be uniform randomly distributed and suddenly their "test group" was 15% instead of the intended 1%. better generate a truely random value using your languages favorite crypto functions and be able to work with it without fear of busting production
If you mod by anything other than a power of two, it won't be. https://lemire.me/blog/2019/06/06/nearly-divisionless-random...
additional to the other excellent comments they will become non-uniform once you start deleting records. that will break all hopes you might have had in modulo and percentages being reliable partitions because the "holes" in your ID space could be maximally bad for whatever usecase you thought up.
The systems I’ve use pre-allocate users effectively randomly an arm by hashing their user id or equivalent.