Supported Apache Cassandra consistency levels in Amazon Keyspaces - Amazon Keyspaces (for Apache Cassandra)

Supported Apache Cassandra consistency levels in Amazon Keyspaces

The topics in this section describe which Apache Cassandra consistency levels are supported for read and write operations in Amazon Keyspaces (for Apache Cassandra).

Write consistency levels

Amazon Keyspaces replicates all write operations three times across multiple Availability Zones for durability and high availability. Writes are durably stored before they are acknowledged using the LOCAL_QUORUM consistency level. For each 1 KB write, you are billed 1 write capacity unit (WCU) for tables using provisioned capacity mode or 1 write request unit (WRU) for tables using on-demand mode.

Read consistency levels

Amazon Keyspaces supports three read consistency levels: ONE, LOCAL_ONE, and LOCAL_QUORUM. During a LOCAL_QUORUM read, Amazon Keyspaces returns a response reflecting the most recent updates from all prior successful write operations. Using the consistency level ONE or LOCAL_ONE can improve the performance and availability of your read requests, but the response might not reflect the results of a recently completed write.

For each 4 KB read using ONE or LOCAL_ONE consistency, you are billed 0.5 read capacity units (RCUs) for tables using provisioned capacity mode or 0.5 read request units (RRUs) for tables using on-demand mode. For each 4 KB read using LOCAL_QUORUM consistency, you are billed 1 read capacity unit (RCU) for tables using provisioned capacity mode or 1 read request units (RRU) for tables using on-demand mode.

Billing based on read consistency and read capacity throughput mode per table for each 4 KB of reads
Consistency level Provisioned On-demand
ONE 0.5 RCUs 0.5 RRUs
LOCAL_ONE 0.5 RCUs 0.5 RRUs
LOCAL_QUORUM 1 RCU 1 RRU

Unsupported consistency levels

The following consistency levels are not supported by Amazon Keyspaces and will result in exceptions.

Unsupported consistency levels
Apache Cassandra Amazon Keyspaces
EACH_QUORUM Not supported
QUORUM Not supported
ALL Not supported
TWO Not supported
THREE Not supported
ANY Not supported
SERIAL Not supported
LOCAL_SERIAL Not supported