为什么我的解决方案这么慢，如何提高查询性能?

Currently I was able to optimise performance quite a bit, but it is still somewhat slow :/

LATEST EDIT:

My current solution (the fastest atm (but still slow) and keeps order):

server

router.post('/images', function(req, res, next) {
    var image = bucket.file(req.body.image);
    image.download(function(err, contents) {
        if (err) {
            console.log(err);
        } else {
            var resultImage = base64_encode(contents);
            var index = req.body.index;
            var returnObject = {
                image: resultImage,
                index: index
            }
            res.send(returnObject);
        }
    });
});

client query

$scope.getDataset = function() {

                fb.orderByChild('id').startAt(_start).limitToFirst(_n).once("value", function(dataSnapshot) {

                    dataSnapshot.forEach(function(childDataSnapshot) {
                        _start = childDataSnapshot.child("id").val() + 1;

                        var post = childDataSnapshot.val();
                        var image = post.image;

                        var imageObject = {
                            image: image,
                            index: position
                        };
                        position++;
                        $.ajax({
                            type: "POST",
                            url: "images",
                            data: imageObject,
                        }).done(function(result) {
                            post.image = result.image;
                            $scope.data[result.index] = post;
                            $scope.$apply();
                            firstElementsLoaded = true; 
                        });
                    })  
                });
            };

client HTML

<div ng-controller="ctrl">
        <div class="allcontent">
            <div id="pageContent" ng-repeat="d in data track by $index"><a href="details/{{d.key}}" target="_blank"><h3 class="text-left">{{d.title}}<a href="../users/{{d.author}}"><span class="authorLegend"><i> by {{d.username}}</i></span></a></h3>
                </a>
                <div class="postImgIndex" ng-show="{{d.upvotes - d.downvotes > -50}}">
                    <a href="details/{{d.key}}" target="_blank"><img class="imgIndex" ng-src="data:image/png;base64,{{d.image}}"></a>
                </div>
                <div class="postScore">{{d.upvotes - d.downvotes}} HP</div>
            </div>
        </div>
    </div>

解决方案

Your solution is slow because you are downloading the images from your Cloud Storage and serving them on your own server. You get a delay on the download and upload, a ~33% overhead using base64-encoded data, plus your server is strained in delivering images instead of focusing on delivering your website content.

As pointed by many on the comments, the best-practice solution is to use the public URL for the images like so:

function getPublicUrl (filename) {
  return "https://storage.googleapis.com/${CLOUD_BUCKET}/${filename}";
}

By using the public URL, you are directly serving from Cloud Storage leveraging Google’s global serving infrastructure. And the application does not have to respond to requests for images, freeing up CPU cycles for other requests.

If you do not want bots to crawl your images using the above method, Google recommends using a robots.txt file to block access to your images.