PACELC
On This Lesson 4 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
add the trade-off CAP leaves out.
Planned topics
- PACELC: if Partition, choose A or C; Else (normal operation), choose Latency or Consistency.
- Synchronous replication gives stronger consistency but every write waits for replicas.
- Asynchronous replication is faster but replicas lag.
- This is why a read replica can return stale data on a healthy network.
- Real products are configurable; check settings rather than slogans (verify per product before recording).
Draft outline details
Demonstration
| Setup | Normal operation | During partition |
|---|---|---|
| Sync replicas, quorum writes | higher latency, consistent | may reject writes |
| Async read replica | low latency, may be stale | serves stale reads |
Check your understanding
Why can a healthy system still return stale reads?
Show answer
Asynchronous replication trades consistency for latency.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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