Any computation that takes the time can take advantage of caching and return precomputed results faster. However, the problem is stale data or, often, quoted as one of the hardest things in computer science, cache invalidation. This is commonly spotted when, despite refreshing the page, a YouTube video's view count doesn't change.
Django has a flexible cache system that allows you to cache anything from a template fragment to an entire site. It allows a variety of pluggable backends such as file-based or data-based backed storage.
Most production systems use a memory-based caching system, such as Redis or Memcached. This is purely because volatile memory is many orders of magnitude faster than disk-based storage.
Such cache stores ...
