docs: @Override
    public EvictionPolicy.Action evict(Event<T> event) {
      long now =
          evictionContext == null ? System.currentTimeMillis() : evictionContext.getReferenceTime();
      long diff = now - event.getTimestamp();
      if (diff >= (windowLength + delta)) {
        return Action.EXPIRE;
      } else if (diff < 0) { // do not process events beyond current ts
        return Action.KEEP;
      }
      return Action.PROCESS;
    }