diff --git a/storage/PartsHelper.h b/storage/PartsHelper.h
index 6ad4e0b3..e5b773f2 100644
--- a/storage/PartsHelper.h
+++ b/storage/PartsHelper.h
@@ -238,7 +238,7 @@ struct PartsHelper {
         return key() < other.key();
       }
     };
-    std::set<Key> rarest_parts;  // TODO: use vector instead of set
+    std::vector<Key> rarest_parts;  // Using vector for better performance
   };
 
   std::vector<Part> parts_;