So far, this chapter has focused on caching your own data. But another type of caching is relevant to web development, too: caching performed by downstream caches. These are systems that cache pages for users even before the request reaches your website. Here are a few examples of downstream caches:
Your ISP may cache certain pages, so if you requested a page from
http://example.com/
, your ISP would send you the page without having to accessexample.com
directly. The maintainers ofexample.com
have no knowledge of this caching; the ISP sits betweenexample.com
and your web browser, handling all of the caching transparently.Your Django website may sit behind a proxy cache, such as Squid web Proxy Cache (for more information visit http://www.squid-cache.org/), that caches pages for performance. In this case, each request first would be handled by the proxy, and it would be passed to your application only if needed.
Your web browser caches pages, too. If a web page sends out...