Lesson 2.37mIntermediate10.9k students

Consistency models and CAP

When the network partitions you choose consistency or availability. Most real systems pick a different answer per operation.

This lesson sits in Data at Scale, part of System Design Foundations. It assumes what came before it and leads directly into the next lesson in the module.

In this lesson you will

  • Place a system on the consistency spectrum
  • Choose guarantees per operation, not per database
  • Explain the user-visible effect of eventual consistency

Pro tip

Ask what the user sees when a read is stale. That answer picks your consistency model faster than any theorem.

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