Latency is not a single number, it's a distribution. Your 99.9%tile latency will suffer when your GC has a 2s pause every 20 seconds, even when the mean latency

Latency is not a single number, it's a distribution. Your 99.9%tile latency will suffer when your GC has a 2s pause every 20 seconds, even when the mean latency is low. But yes, they also affect mean latency.