Linearizability and Sequential Consistency

The two strongest consistency models in distributed systems — and the real-world cost of guaranteeing that every read returns the most recent write.

Key Takeaways

1. Linearizability means operations appear to take effect at a single instant — every read returns the most recent write, as if there's one copy of the data
2. Sequential consistency means all nodes see operations in the same order — but that order may not match real-time wall-clock ordering
3. Linearizability is stronger and more expensive than sequential consistency — it requires coordination across nodes on every operation
4. Use linearizability for correctness-critical operations — leader election, lock acquisition, unique constraint checks
5. Most distributed databases offer configurable consistency levels — letting you choose the trade-off per operation