Concurrency queries performance issue


We observe some slow answers by Druid when we have concurrents queries.
For instance, I could have a query A which lasts about 1s but when I do the query A 10x it lasts about 30s!
Which parameters impact the speed answer in this case?
We use Apache Druid 0.21.1

This post is a good place to start, but it is long and fairly comprehensive:

The docs also have something to say here. If you have already applied these, please respond with more details about your cluster set up:

Basic Guidelines:

On Broker RunTime Properties –

  1. Set to Number of Available Cores, as a starting point
  2. Set druid.processing.buffer.sizeBytes to 500MB to 1GB. If you set it to higher value, please make sure you have enough available memory on the instances.

On Historical and Task RunTime Properties –

  1. Set druid.server.http.numThreads to Number of Query Nodes x
  2. Set druid.processing.buffer.sizeBytes= 500MB to 1GB. Try and keep this in sync with the values on Broker Service.

If you start seeing TOO MANY OPEN FILES. Please increase ulimit size, at the time of Service start.