CAP Theorem (Brewer's theorem)

The CAP Theorem states that in a distributed system, it’s impossible to simultaneously guarantee all three qualities: Consistency (all nodes see the same data), Availability (the system is operational and responds to requests), and Partition Tolerance (the system continues functioning despite network failures). When a network partition occurs, you must choose between maintaining consistency or availability. This trade-off helps designers decide how to prioritize these qualities based on the system’s needs—either ensuring data stays accurate or that the system remains accessible during issues.