Firebase is like mongodb, there are cases when you can use the ref.once('value') to get a unsorted object without having synchronization, but when you need a order array of objects, the way to avoid concurrent connections is this:

destroy-the-synchronization.js

var fireData = {
 locations: {}
};

      // Create a synchronized array, and then destroy the synchronization after having the data
      var locations = $firebaseArray(FireRef.child('locations').orderByChild('left'));
      locations.$loaded()
        .then(function () {
          fireData.locations = angular.copy(locations);
          locations.$destroy();
        });