Slick confused about numThreads and best practice for good performannce

[Ignacio Hernandez]

I am using the PlayFrameWork with slick and using it in a system that is all I/O database heavy. In my application.Conf file I have this setting

play {
  akka {
    akka.loggers = ["akka.event.slf4j.Slf4jLogger"]
    loglevel = WARNING
    actor {
      default-dispatcher = {
        fork-join-executor {
          parallelism-factor = 20.0
     
        }
      }
    }
  }
}

This obviously gives me 20 threads per core for the play application and as I understand it Slick creates it's own threadpool, is the NumThreads field in Slick mean that that's the total number of threads or is it (NumThreads x CPU's) ? and is there any best practice for best performance ? I currently have my settings configured as

database {
  dataSourceClass = "org.postgresql.ds.PGSimpleDataSource"
  properties = {
    databaseName = "dbname"
    user = "postgres"
    password = "password"

  }
  numThreads = 10

}