code: public boolean isExpired() {
      if (_service.getTtl() == 0) {
        return false;
      }
      long t = this.cacheStartTime.getTime();
      Date validTime = new Date(t + (_service.getTtl() * ONE_MINUTE_IN_MILLIS));
      Date now = new Date();
  
      return (now.getTime() > validTime.getTime());
    }
docs: Determine if the service record is expired. The service record include a
  TTL that tells the client how many minutes the client can count on the
  information in the service record. If the cache times out, then those
  service records that have expired should be expunged from the cache.
  
  @return true if the service record should be expired from the cache