One of the best kept "secret" of Fatwire is the cache invalidation mechanism.
Really slow. It is slow because there are many database queries involved. So, once a template is rendered, the result is cached (at least, if you have enabled caching for that template).
But, when you cache a component, what happens if the source asset change? I mean, what happens if you render an article, and then the article is updated? Of course, when the source asset is updated the cached element is invalidated.
There is actually a database table tracking all the dependencies. For each cached element (called "pagelet") in the database, a dependency is stored in that table. That is, the information:
"which pagelet must be invalidated when an asset is updated".
When you publish it happens that the cache is updated, as well.
For each published asset,
1. all the dependencies are searched for
2. all the cached pagelet that depends on the published asset are invalidated.
Please note that this happens only for the pagelets that have dependencies on the published assets.
So you don't need to rebuild the whole cache, but only the pagelet that are invalidated. Just a bunch of them. Those who depends on the new assets.
It is a smart and powerful mechanism. Unfortunately, is is also a mechanism easy to break if you don't follow a design and some simple rules in coding templates.
Or worse, if you ignore the caching and the dependency mechanism.
