[TiddoLangerak]

This is only true if your latency distribution is fully random, which is rarely the case. More often than not, it's the same small group of users hitting most of the p99 because their accounts are simply more resource intensive.

[the8472]

Depending on how the system distributes work such users can interfere with random with requests from other users through shared resources, so to that cohort these will look like a random latency distribution.