// none of the remaining methods are actually required by the cache directive - but they must be implemented to
  // satisfy the spray Cache trait. The equivalent methods offered by ConcurrentLinkedHashMap appeared to be async, but
  // with Caffeine we need to use the synchronous view.

  def remove(key: Any) = {
    Option(store.synchronous().asMap().remove(key)).map(value => Future.successful(value))
  }

  def clear(): Unit = store.synchronous().invalidateAll()

  def keys: Set[Any] = store.synchronous().asMap().keySet().asScala.toSet

  def ascendingKeys(limit: Option[Int] = None) = ???

  def size = store.synchronous().asMap().size()def remove(key: Any) = {
    Option(store.synchronous().asMap().remove(key)).map(value => Future.successful(value))
  }