Exploring NoSQL repositories
NoSQL is an umbrella term comprising a number of very different data storage technologies. The term was coined mostly for marketing purposes in order to distinguish them from relational databases. Some NoSQL databases even support SQL-like query languages. NoSQL databases claim to outdo relational databases in terms of performance. However, this assurance only exists because of some compromises, namely the lack of some features, usually in terms of transactionality and reliability. But to discuss these limitations, it is worth having an overview of the CAP theorem.
The CAP theorem
The CAP theorem was theorized by Eric Brewer in 1998 and formally proven valid in 2002 by Seth Gilbert and Nancy Lynch. It refers to a distributed data store, regardless of the underlying technology, so it's also applicable to relational databases when instantiated in a multi-server setup (so, running in two or more different processes, communicating through a network...
