Added limit on select as for the outcome it doesn't matter if there are 20 rows or just 1. Is sufficient to return straight after reading 1 row.

modules/gallery/libraries/drivers/Cache/Database.php

@@ -34,6 +34,7 @@ class Cache_Database_Driver extends Cache_Driver {
     $count = db::build()
       ->where("key", "=", $id)
       ->where("expiration", ">=", time())
+      ->limit("1")
       ->count_records("caches");
     return $count > 0;
   }