optimisations (cut down on category queries, cut down on expensive current_user query)

app/serializers/current_user_serializer.rb

@@ -25,7 +25,7 @@ class CurrentUserSerializer < BasicUserSerializer
   end
 
   def reply_count
-    object.posts.where("post_number > 1").count
+    object.topic_reply_count
   end
 
   def site_flagged_posts_count

app/serializers/topic_list_item_serializer.rb

@@ -14,7 +14,7 @@ class TopicListItemSerializer < ListableTopicSerializer
              :rank_details,
              :excerpt
 
-  has_one :category
+  has_one :category, serializer: BasicCategorySerializer
   has_many :posters, serializer: TopicPosterSerializer, embed: :objects
 
   def starred