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 |
