Caching paginated results, purging on update - how to solve?

Question

I\'ve created a forum, and we\'re implementing an apc and memcache caching solution to save the database some work.

I started implementing the cache layer with keys like

Answer 1

Just an update: I decided that Josh's point on data usage was a very good one. People are unlikely to keep viewing page 50 of a forum.

Based on this model, I decided to cache the 90 latest threads in each forum. In the fetching function I check the limit and offset to see if the specified slice of threads is within cache or not. If it is within the cache limit, I use array_slice() to retrieve the right part and return it.

This way, I can use a single cache key per forum, and it takes very little effort to clear/update the cache :-)

I'd also like to point out that in other more resource heavy queries, I went with flungabunga's model, storing the relations between keys. Unfortunately Stack Overflow won't let me accept two answers.

Thanks!