AkkaTypedRateLimiter.scala

def rateLimit(timer: TimerScheduler[RateLimiterMsg], 
  data: RateLimiterQueue[LazyFuture]): Behavior[RateLimiterMsg] =
    Behaviors.receiveMessage {
      case lf: LazyFuture    => rateLimit(timer, runQueue(timer, data.enqueue(lf)))
      case ScheduledRunQueue => rateLimit(timer, runQueue(timer, data.notScheduled))
    }

def runQueue(timer: TimerScheduler[RateLimiterMsg], 
  data: RateLimiterQueue[LazyFuture]): RateLimiterQueue[LazyFuture] = {

  val now = System.currentTimeMillis()

  val (tasks, data2) = data.run(now)
  tasks.foreach {
    case Run(LazyFuture(f)) => f()
    case RunAfter(millis)   => timer.startSingleTimer((), ScheduledRunQueue, 
                                                      millis.millis)
  }

  data2
}