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Data & Analytics · Advanced

Tunable Consistency

The ability to choose, per operation or per account, how many replicas must acknowledge a read or write.

Definition

In Cassandra, if read replicas + write replicas > replication factor (for example QUORUM reads and writes), reads see the latest write. Cosmos DB exposes five levels: Strong, Bounded Staleness, Session, Consistent Prefix and Eventual.

Exam tip

R + W > N gives strong consistency in quorum-based systems.

Related terms