diff --git a/db/migrate/20140910130155_create_topic_user_index.rb b/db/migrate/20140910130155_create_topic_user_index.rb
new file mode 100644
index 00000000000..0f02e645348
--- /dev/null
+++ b/db/migrate/20140910130155_create_topic_user_index.rb
@@ -0,0 +1,6 @@
+class CreateTopicUserIndex < ActiveRecord::Migration
+  def change
+    # seems to be the most effective for joining into topics
+    add_index :topic_users, [:user_id, :topic_id], unique: true
+  end
+end