Why is Round Robin bad for 95th & 99th percentile

We see that round robin doesn’t perform well in the higher percentiles. How can it be that round robin has a great median, but bad 95th and 99th percentiles?

In round robin, the state of each server isn’t considered, so you’ll get quite a lot of requests going to servers that are idle. This is how we get the low 50th percentile. On the flip side, we’ll also happily send requests to servers that are overloaded, hence the bad 95th and 99th percentiles.

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