Cache Category Data VqMod for Opencart v.3.x to make it faster. http://forum.opencart.com/viewtopic.php?f=161&t=126241

cache_category_data.xml

<modification>

    <id>Cache category data to speed up page load for store with many categories and sub categories.</id>
    <version>1.0.1</version>
    <vqmver>2.3.2</vqmver>
    <author>Weismann Web - www.weismannweb.com</author>

    <file name="catalog/controller/extension/module/category.php">
        <operation>
            <search position="after"><![CDATA[
            foreach ($categories as $category) {
            ]]></search>
            <add><![CDATA[
						$category_data = $this->cache->get('vqmod_category_data_controller_module_category_'.$data['category_id'].'_'.$this->config->get('config_store_id'));
	
		    if ($category_data) {
		        $data['categories'] = $category_data;
			    break;
		    }
            ]]></add>
        </operation>
        <operation>
            <search position="replace"><![CDATA[
            return $this->load->view('extension/module/category', $data);
            ]]></search>
            <add><![CDATA[
            if (empty($category_data)) {
			          $this->cache->set('vqmod_category_data_controller_module_category_'.$data['category_id'].'_'.$this->config->get('config_store_id'), $data['categories']);
			        }
              
            return $this->load->view('extension/module/category', $data);
            ]]></add>
        </operation>
    </file>

 <file name="catalog/controller/common/menu.php">
        <operation>
            <search position="after"><![CDATA[
            foreach ($categories as $category) {
            ]]></search>
            <add><![CDATA[
            $category_data = $this->cache->get('vqmod_category_data_controller_common_header'.$this->config->get('config_store_id'));
	
		    if ($category_data) {
		        $data['categories'] = $category_data;
			    break;
		    }
            ]]></add>
        </operation>
        <operation>
            <search position="replace"><![CDATA[
            return $this->load->view('common/menu', $data);
            ]]></search>
            <add><![CDATA[
            if (empty($category_data)) {
			$this->cache->set('vqmod_category_data_controller_common_header'.$this->config->get('config_store_id'), $data['categories']);
			}
      return $this->load->view('common/menu', $data);
            ]]></add>
        </operation>
    </file>

 
</modification>