SlidingWindow.scala

      case class SomeEvent(value: Long)

      val events = Source
        .tick(0 seconds, 250 millis, "")
        .zipWithIndex
        .map { case (_, l) =>
            SomeEvent(l)
        }

      val group = Flow[SomeEvent].groupedWithin(100, 500 millis) // +/- 2 events per group
      val slide = Flow[Seq[SomeEvent]].sliding(3, 1) // 3 groups per slide, step size = 1
      val exe = events
        .via(group)
        .via(slide)
        .map(_.flatten)
        .runWith(Sink.foreach(println))

      try Await.result(exe, 6 seconds)
      catch { case _: Throwable => }