APC (Alternative PHP Cache) is an opcode cache for PHP that works very well to speed up page loads when used on servers running Magento. There are many opcode caches available (APC, accelerator, xcache, etc) which can be used with Magento, but we will be focusing on APC here as it along with eAccelerator are recommended by Magento in their performance whitepapers. eAccelerator also works very well with Magento, but please note that you must use version 0.9.5 or older.
APC can be used for two purposes within Magento. The first is as an opcode cache that PHP will utilize to cache any PHP files that are compiled through it. APC can also be utilized by Magento as an fast backend cache for Magento data. This can be configured within the Magento local.xml. Read morePosted in: Magento, php