code: function KeyStatus (options) {
    options = utils.clone(options || {});
    var id = this.id = options.id || utils.uniqueId('keys');
    var debug = this._debug = utils.debug('keys:' + id);
    this._keys = {};
    var me = this;
  
    options.interval = options.interval || define.keysStatusScanInterval;
    me._tid = setInterval(function () {
      me._debug('scan expired keys');
      var now = Date.now();
      for (var k in me._keys) {
        var v = me._keys[k];
        if (v > 0 && v < now) {
          me._debug('key expired: %s, %s', k, v);
          delete me._keys[k];
        }
      }
    }, options.interval);
  }
docs: KeyStatus
  
  @param {Object} options