Simple parallel composition of Future with max parallelism in a sliding window

a.scala

import akka.stream.Materializer
import akka.stream.scaladsl._
import scala.concurrent.{Future, ExecutionContext}

// This will execute futures in parallel with a max parallelism
def traverse[A, B](as: Seq[A], parallelism: Int)(f: A => Future[B])
                  (implicit ec: ExecutionContext, mat: Materializer): Future[Seq[B]] = {
  Source(as.toList)
    .mapAsync(parallelism)(f)
    .runWith(Sink.seq)
}