Just to add the other good answers already provided, there are some tricks to get the cake, to use anything other than the file cache to cache it internally. This code will make use of the APC cake, Xcache, regardless of its main cache (APC in this example)
Cache::config('_cake_core_', array( 'engine' => 'Apc', 'duration'=> 3600, 'probability'=> 100, ) );
Cake can also cache your models by putting them in their controllers / applications.
var $persistModel = true;
However, models can use the file cache.
All of them were stolen from this article, which includes many ways to use cache-caching mechanisms to speed up your application.
http://www.pseudocoder.com/archives/8-ways-to-speed-up-cakephp-apps
In addition, as Pascal noted, by installing and configuring APC, your PHP operation code is automatically cached.
For even greater caching convenience, php supports memcache as an alternative to files as a session repository, which is especially useful in a load-balanced environment. An example of a single server implementation would be to put this in your ini
extension=memcache.so session.save_handler = memcache session.save_path = "tcp://127.0.0.1:11211?persistent=1"
And this is in your core.php
Configure::write('Session.save', 'php');