Tell me about the CAP theorem.

The CAP theorem states that a distributed system cannot simultaneously guarantee all three properties: Consistency, Availability, and Partition tolerance.

• Consistency: all nodes see the same data at the same time.
• Availability: every request receives a response (successful or error) without long delays.
• Partition tolerance: the system continues to operate despite network partition failures.

In real-world conditions, when a network partition occurs, the system must choose between consistency and availability. For example, a database can either refuse to respond to maintain consistency or return outdated data to preserve availability.

This is a fundamental limitation in designing distributed systems, affecting architecture choices and trade-offs.