Cache busting (also known as cache bursting, cache flushing, or cache invalidation) is the hard part of caching. It is easy to put an item in a cache, but if you don't have a strategy ahead of time to manage the inevitable change, then you may come unstuck.
Getting cache busting correct is usually more important with web-level caching. This is because, with server-side caching (which we'll discuss later in this chapter), you are in full control and can reset if you get it wrong. A mistake on the web can persist and be difficult to remedy.
In addition to setting the correct headers, it is helpful to vary the URL of resources when their content changes. This can be done by adding a timestamp, but often, a convenient solution is ...
