# Consistency Models (multi-replicas)
+ Strong consistency
  + Once data is written, the new value can be observed at any time in any replica
+ Weak consistency
  + After data is written, the new value can either be observed or not be observed on other replicas, there is no guarantee
+ Eventual consistency
  + After data is written, the new value may not be observed, but it is guaranteed to be observed after a certain time window
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