Сортировка сущностей и фильтрация ListProperty без увеличения индексов

Я разрабатываю простую платформу для ведения блогов / закладок и пытаюсь добавить функцию tag-explorer / Drill-Down là Delicious , чтобы пользователи для фильтрации сообщений с указанием списка конкретных тегов.

Примерно так:

Posts are represented in the datastore with this simplified model:

class Post(db.Model):
    title = db.StringProperty(required = True)
    link = db.LinkProperty(required = True)
    description = db.StringProperty(required = True)
    tags = db.ListProperty(str)
    created = db.DateTimeProperty(required = True, auto_now_add = True)

Post's tags are stored in a ListProperty and, in order to retrieve the list of posts tagged with a specific list of tags, the Post model exposes the following static method:

@staticmethod
def get_posts(limit, offset, tags_filter = []):
        posts = Post.all()
        for tag in tags_filter:
          if tag:
              posts.filter('tags', tag)
        return posts.fetch(limit = limit, offset = offset)

This works well, although I've not stressed it too much.

The problem raises when I try to add a "sorting" order to the get_posts method to keep the result ordered by "-created" date:

@staticmethod
def get_posts(limit, offset, tags_filter = []):
        posts = Post.all()
        for tag in tags_filter:
          if tag:
              posts.filter('tags', tag)
        posts.order("-created")
        return posts.fetch(limit = limit, offset = offset)

The sorting order adds an index for each tag to filter, leading to the dreaded exploding indexes problem.
One last thing that makes this thing more complicated is that the get_posts method should provide some pagination mechanism.

Do you know any Strategy/Idea/Workaround/Hack to solve this problem?