The concept of caching is simple, in that it provides pre-processed result sets for oft-used queries (often referred to as static data). These result sets can be extracted from the database and be provided to the end user in some alternate manner. In principle:

• Eliminating repeated requests for static data reduces load on the the server and allows it to serve transactional data more efficiently.

However, in practice, improvements in database servers, disk drives and memory have made it difficult to obtain improvements in performance unless:

• The performance of the underlying system is extremely poor, for example in Microsoft Access Databases (although this is a poor solution in the first place for this kind of system).
• All incremental improvements are considered appropriate, for example in high-volume OLTP environments.

In this situation, each of the above situations can be considered as a different configuration issue.

ADOdb provides 2 distinct solutions to the underlying configuration:

1. A traditional, simple disk based caching system that can be installed locally
2. A remote memory caching server based on Memcached

Once implemented, the coding methodologies are the same.