CAP theorem, also known as Brewer’s theorem, was introduced by Eric Brewer in 1998 as conjecture.
In 2002, it was proven as a theorem by Seth Gilbert and Nancy Lynch.
A Complete Guide to Understanding This Blockchain Concept
The theory states that any distributed system cannot have consistency, availability, and partition tolerance simultaneously: Consistency is a property which ensures that all nodes in a distributed system have a single, current, and identical copy of the data.
Availability means that the nodes in the system are up, accessible for use, and are accepting incoming requests and responding with data without any failures as and when required.
In other words, data is available at each node and the nodes are responding to requests.
Partition tolerance ensures that if a group of nodes is unable to communicate with other nodes due to network failures, the distributed system continues to operate correctly.
It has been proven that a distributed system cannot have consistency, availability, and partition tolerance simultaneously.
Let’s imagine that there is a distributed system with two nodes.
Why This Matters for Blockchain Technology
Now let us apply the three theorem properties on this smallest of possible distributed systems only with two nodes.
Consistency is achieved if both nodes have the same shared state; that is, they have the same up-to-date copy of the data.
Availability is achieved if both nodes are up and running and responding with the latest copy of data.
Partition tolerance is achieved if communication does not break down between two nodes (either due to network issues, Byzantine faults, and so forth), and they are able to communicate with each other.
Key Points to Remember
- CAP theorem and blockchain CAP theorem, also known as Brewer’s theorem, was introduced by Eric Brewer in 1998 as conjecture.
- In 2002, it was proven as a theorem by Seth Gilbert and Nancy Lynch.
- The theory states that any distributed system cannot have consistency, availability, and partition tolerance simultaneously: Consistency is a property which ensures that all nodes in a distributed system have a single, current, and identical copy of the data.
- Availability means that the nodes in the system are up, accessible for use, and are accepting incoming requests and responding with data without any failures as and when required.
Going Deeper: Advanced Concepts
Now think of scenario where a partition occurs and nodes can no longer communicate with each other.
If no new updated data comes in, it can only be updated on one node only.
In that case, if the node accepts the update, then only that one node in the network is updated and therefore consistency is lost.
Now, if the update is rejected by the node, that would result in loss of availability.
Conclusion
CAP theorem and blockchain represents one of the many innovative layers that make blockchain technology so powerful and transformative. As distributed systems continue to evolve, a solid understanding of these core concepts becomes increasingly valuable — not just for developers, but for anyone building, investing in, or working alongside blockchain-powered systems.
Whether you are just starting your blockchain journey or deepening existing expertise, mastering these fundamentals gives you the tools to think clearly about decentralized systems and make smarter decisions in this rapidly evolving space.