Causal Consistency
Causal consistency guarantees that causally related operations become visible in causal order, while concurrent unrelated operations may be seen in any order.
Purpose
To provide a stronger guarantee than eventual consistency in scenarios that need causal correctness but not strong consistency.
Mechanism
Vector clocks or version vectors track causality. If operation A causally precedes B (B read or learned of the value A wrote), all nodes see A before B. Concurrent operations may appear in different orders.
Use cases
- Collaborative editing
- Social comment systems
- Causal history tracking