You have 4 caching method options available in stock opencart.
File cache is the default and it dos not accelerate the system. then there are apc and memcached. where memcached generally is the method that has the largest performance boost.
But you have to make sure your webhost provider has memcache installed and available on your hostingplan.
You can create a new file on your webspace with the code below, and set your browser to it http://www.yourshop.com/php.php and then it wil give you the information about memcached. it is a long list so you can use ctrl+f to search for memcached. remember to delete the file efter you have searched it.
You need some information in order to use memcached
How to enable
You need to manually edit system/config/default.php (opencart 3)
// Cache $_['cache_engine'] = 'apc'; // apc, file, mem or memcached $_['cache_expire'] = 3600;
And if you choose to use memcached you need to set up the server details obtained from your hostingprovider in file in root named config.php
//cache define('CACHE_HOSTNAME', '127.0.0.1'); define('CACHE_PORT', '11864'); define('CACHE_PREFIX', 'oc_');