Filter on prefetch_related in Django

It is very simple method which is hardly comparable with those app, but hope you will find it useful:

class Author(models.Model):
    name = models.CharField(max_length=100)

    def latest_book(self):
        return max(self.book_set.all(), key=lambda book: book.created)

authors = Author.objects.prefetch_related('book_set')
authors[0].latest_book() #  what you wanted

As of Django 1.7, filtering prefetched objects is possible. See this SO answer, and the Django documentation.