diff --git a/boards/models/post.py b/boards/models/post.py
--- a/boards/models/post.py
+++ b/boards/models/post.py
@@ -25,6 +25,7 @@ APP_LABEL_BOARDS = 'boards'
 
 CACHE_KEY_PPD = 'ppd'
 CACHE_KEY_POST_URL = 'post_url'
+CACHE_KEY_OPENING_POST = 'opening_post'
 
 POSTS_PER_DAY_RANGE = range(7)
 
@@ -271,7 +272,7 @@ class Post(models.Model):
         return self.referenced_posts.all().exists()
 
     def is_opening(self):
-        return self.thread_new.get_replies()[0] == self
+        return self.thread_new.get_opening_post() == self
 
     def save(self, *args, **kwargs):
         """
@@ -430,7 +431,13 @@ class Thread(models.Model):
         Get first post of the thread
         """
 
-        return self.get_replies()[0]
+        cache_key = CACHE_KEY_OPENING_POST + str(self.id)
+        opening_post = cache.get(cache_key)
+        if not opening_post:
+            opening_post = self.get_replies()[0]
+            cache.set(cache_key, opening_post)
+
+        return opening_post
 
     def __unicode__(self):
         return str(self.id)