Definition - What does CAP Theorem mean?
Techopedia explains CAP Theorem
Many attribute the CAP theorem to the work of computer scientist Eric Brewer around the turn of the century. MIT academics have published supporting pieces for this theory.
The CAP theorem is at the heart of conversations about different models for data distribution in computer systems. Experts point out that this theory about limited resources is part of what drives a look at alternative methods for enforcing data consistency and other principles.
Part of the idea of the CAP theorem regards the enforcement of two different data models. The first one is Atomicity, Consistency, Isolation and Durability, or ACID. This property set enforces reliable data transactions. However, as some have pointed out, the idea of the CAP theorem has led to the popularity of models like Basically Available Soft State Services with Eventual Consistency - in this model, consistency is sacrificed for other priorities.
Another way to think about the CAP theorem is that it's in some ways similar to the old tradesmen's motto of availability for trade services -- this colloquial saying claims that you can have services cheap, fast and of good quality, but not all three. This points to the same kind of idea of limited resources and results that the CAP theorem points to in computer science. The CAP theorem has also been used in analysis of new data analysis projects using technologies like Hadoop to work with massive sets of organized and less organize data for enterprise IT.
Another point about the CAP theorem has to do with the definition of 'availability’. Experts point out that you can have a system that's considered 'high availability’ without having all parts of the database available at all times. This is one of several fixes for the idea of balancing consistency and availability in data transactions.