Explain what the cache invalidation process means and why it is used in data storage systems.

Cache invalidation is the process of removing or marking outdated data in the cache as invalid. This is necessary so that when data is next accessed, the system does not use stale information but loads the current data from the primary source.

In data storage systems, cache invalidation is used to maintain consistency between the cache and the main database or file system. For example, if data in the database changes, the corresponding cached copies need to be invalidated to prevent serving outdated information to the user.

Without cache invalidation, inconsistent or incorrect data may be retrieved, which is especially critical for systems with frequent updates.