@mark thank you for this topic. I have already arranged VUs in my test to be unique as was required for our platform performance testing.
The last point that I can’t get it’s how to distribute VUs uniqueness when multiple instances (e.g load generators) are raised. 
Initially, we need to mimic 3K unique users, but currently started from 500, so following the context of 500 users and as I understand, as soos as my cloud test will reach out 300 VUs - it will be raised the second insntance which will start generating duplicated VU IDs.
How to correctly make the calculation?
let uniqueNum = ((__VU * maxIter) - (maxIter) + (__ITER) + (80000 * __ENV["LI_INSTANCE_ID"])); - can’t relate this formula for my test.
For instance, we have to run 500 VU’s(unique accounts, where email has index from 1 to 500) for 1 hour, I don’t know how many iterations it will be, also I don’t know the ID of “LI_INSTANCE_ID”?