Causal Consistency

A practical middle ground between strong and eventual consistency — preserving cause-and-effect ordering without the performance cost of linearizability.

Key Takeaways

1. Causal consistency preserves the order of causally related operations — if A causes B, everyone sees A before B
2. Concurrent (unrelated) operations may be seen in any order — this is weaker than linearizability but much cheaper to implement
3. Vector clocks or Lamport timestamps track causal dependencies — enabling the system to enforce ordering only where it matters
4. Causal consistency is a practical middle ground — stronger than eventual consistency, cheaper than linearizability