ALL

Queries return the most recent data from all replica nodes in the cluster. All replica nodes must must respond.

This read consistency level provides the highest consistency, the highest latency, and the lowest availability of any level.

QUORUM

Queries return the most recent data from a quorum of replica nodes across all datacenters.

Cross-datacenter communication may incur extra latency.

ONE

Queries return data from the closest replica.

Use for high availability and low consistency.

TWO

Queries return the most recent data from two of the closest replicas. Two replica nodes must respond.

Similar to ONE.

THREE

Queries return the most recent data from three of the closest replicas. Three replica nodes must respond.

Similar to TWO.

LOCAL_QUORUM

Queries returns the most recent data from a quorum of replicas in the current datacenter. LOCAL_QUORUM avoids latency of cross-datacenter communication.

Use LOCAL_QUORUM to maintain consistency within a single datacenter in a multiple-datacenter cluster.

EACH_QUORUM

Queries return the most recent data from a quorum of replica nodes in each datacenter has responded.

Use EACH_QUORUM in multiple datacenter clusters to ensure data consistency at the same level in each datacenter. Queries will fail if any datacenter fails to achieve a quorum.

LOCAL_ONE

Queries return data from the closest replica node in the local datacenter.

Use LOCAL_ONE to achieve a consistency level of ONE without cross-datacenter communications.

SERIAL

Read consistency level SERIAL is a special case for querying data that may be involved in in-flight lightweight transactions.

Use to achieve linearizable consistency for lightweight transactions.

LOCAL_SERIAL

Read consistency level LOCAL_SERIAL is the same as SERIAL, but confined to the local datacenter.

Use to achieve linearizable consistency for lightweight transactions.