interface Throttle {
  boolean isOkToProcess();
  void processed();
  void processed(long when);
}

class Processor {
  Throttle throttle = ThrottleFactory.defaultThrottle();
  DownstreamProcessor downstream;
  onEvent(Event ev) {
    if (throttle.isOkToProcess()) {
     downstream.process();
     throttle.processed();
    }
}