)
  }

  class RealBackend(
    threadFactory: ThreadFactory,
  ) : Backend {
    val executor =
      ThreadPoolExecutor(
        // corePoolSize:
        0,
        // maximumPoolSize:
        Int.MAX_VALUE,
        // keepAliveTime:
        60L,
        TimeUnit.SECONDS,
        SynchronousQueue(),
        threadFactory,
      )

    override fun nanoTime() = System.nanoTime()