Definition
Linearizability requires operations to appear atomic in real time, while sequential consistency requires a single global order that may not match wall-clock timing.
Key Concepts
- Linearizability is a real-time correctness property.
- Sequential consistency preserves program order, not real-time order.
- Both are stronger than causal and eventual models.
- Cost increases with coordination and latency sensitivity.
How It Works
Linearizable systems coordinate on each operation boundary; sequential systems can reorder non-conflicting operations as long as a legal single order exists.
Comparison Table
| Aspect | Linearizable | Sequential |
|---|---|---|
| Real-time order | Required | Not required |
| Global order | Yes | Yes |
| Latency impact | Higher | Medium |
Production Implications
Linearizability is critical for lock services and control planes. Sequential consistency can be sufficient for some replicated state machines with lower coordination pressure. Dynamo and Cassandra are generally configured below these levels for data-plane throughput.
When to Use / Not Use
Use It When
- Lease management, distributed locks, and leader transitions.
- Invariant-heavy workflows where stale reads are unacceptable.
Avoid It When
- High-throughput social interactions with loose correctness needs.
- Telemetry ingestion where approximate recency is acceptable.
Key Takeaways
- Start with user-visible correctness requirements, then choose the weakest model that still preserves them.
- Instrument staleness and conflict rates; treat them as first-class production metrics.
- Design reconciliation and repair workflows before incidents force ad-hoc fixes.