C H A P T E R  3

Content Caching: Keeping the Load Light

Caching is one of the key ingredients for an awesomely fast and responsive web site. Yet it’s often neglected. It’s not that caching is particularly difficult or hard to set up, but it’s a very broad topic so it’s often hard to know where to start. Caching requires a fair bit of background knowledge because as soon as you start using it, you’re inviting all sorts of potential problems that will be a real nightmare to track down if you’re not up to speed. Actually, even if you know exactly what you’re doing, trying to diagnose issues caused by various different layers of caching and how they may (or may not) interact can drive anyone mad.

Technical books naturally keep pretty close to their core themes. If you buy a book on PHP programming, for example, you would likely be surprised to find a chapter dedicated to Perl or Ruby on Rails. However, when an author wants to introduce caching, they have to compromise: they need to cover enough content to make it useful but it’s quite easy to get mired in technical detail that seems important (and under certain circumstances is essential) yet detracts from the main ideas. This is one reason why many books don’t touch on the topic at all or gloss over it when they do. Thus many developers end up without a solid understanding of what caching is and when and how to use it.