The CAP Theorem

The CAP Theorem states that in a distributed computer system, you can only have two of these three qualities at once: Consistency (all users see the same data), Availability (the system is always operational and responsive), and Partition Tolerance (the system continues to function despite network failures). When a network issue occurs, the system must choose to either stay consistent but become unavailable, or remain available but potentially show different data to users. This trade-off guides system design based on what is more important for that specific application.