Index: app/code/core/Mage/Admin/Model/Variable.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- app/code/core/Mage/Admin/Model/Variable.php	(revision 2bd128c1f190cd9ea63269824f09789199565251)
+++ app/code/core/Mage/Admin/Model/Variable.php	(revision )
@@ -30,6 +30,13 @@
 class Mage_Admin_Model_Variable extends Mage_Core_Model_Abstract
 {
     /**
+     * List of loaded variables
+     *
+     * @var array
+     */
+    static protected $_variables = array();
+
+    /**
      * Initialize variable model
      */
     protected function _construct()
@@ -71,10 +78,12 @@
      */
     public function isPathAllowed($path)
     {
-        /** @var Mage_Admin_Model_Resource_Variable_Collection $collection */
-        $collection = Mage::getResourceModel('admin/variable_collection');
-        $collection->addFieldToFilter('variable_name', array('eq' => $path))
-            ->addFieldToFilter('is_allowed', array('eq' => 1));
-        return $collection->load()->count();
+        if (array_key_exists($path, self::$_variables)) {
+            return self::$_variables[$path];
+        }
+        $result = $this->_getResource()->isPathAllowed($path);
+        self::$_variables[$path] = $result;
+
+        return $result;
     }
 }
Index: app/code/core/Mage/Admin/Model/Resource/Variable.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- app/code/core/Mage/Admin/Model/Resource/Variable.php	(revision 2bd128c1f190cd9ea63269824f09789199565251)
+++ app/code/core/Mage/Admin/Model/Resource/Variable.php	(revision )
@@ -40,4 +40,24 @@
     {
         $this->_init('admin/permission_variable', 'variable_id');
     }
+
+    /**
+     * Check is config directive with given path can be parsed via configDirective method
+     *
+     * @param string $path
+     * @return int
+     */
+    public function isPathAllowed($path)
+    {
+        $adapter = $this->_getReadAdapter();
+        $select  = $adapter->select()
+            ->from($this->getMainTable(), 'COUNT(1)')
+            ->where('variable_name = :variable')
+            ->where('is_allowed = 1');
+        $bind    = array(
+            ':variable' => $path,
+        );
+
+        return $adapter->fetchOne($select, $bind);
+    }
 }