Do you remember the CAP theorem?

The CAP theorem states that a distributed system cannot simultaneously guarantee all three properties:

• Consistency — all nodes see the same data at the same time.
• Availability — every request receives a response, even if part of the system is unavailable.
• Partition tolerance — the system continues to operate despite network partitions.

According to the theorem, during a network partition, the system can guarantee either consistency or availability, but not both at the same time.

For example, in a database during a network failure, one can choose to:

• Ensure consistency by denying responses to some nodes (losing availability).
• Ensure availability by allowing writes on different nodes with possible data inconsistency.

In real systems, compromises are often made, choosing an appropriate CAP balance depending on requirements.