hard20 pts · first answer countslatencymonitoring

Combining percentiles from many servers

Ten servers each report their own p99 latency as a single number. A dashboard averages these ten values to show "service p99". What is the problem?

A.Nothing; the average of p99 values equals the overall p99B.The average is always exactly 10 times too highC.It only works if the servers run different code versionsD.Percentiles cannot be averaged meaningfully; the true overall p99 depends on the full distributions, so you need to merge histograms or raw data

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