Cassandra's Consistency Levels
Understand how Cassandra manages consistency through configurable read and write levels to meet different application needs. Learn how strategies like ALL, QUORUM, and ONE impact data availability and latency. Explore Cassandra's mechanisms such as hinted handoff, read repair, and anti-entropy repair that support high availability and data convergence despite node failures or partitions.
When Cassandra nodes communicate with clients they can specify different consistency levels, which allows them to optimize for consistency, availability, or latency accordingly.
The client can define the desired read consistency level and the desired write consistency level, where each consistency level provides different guarantees.
Consistency levels
Some of the available consistency levels are as follows:
ALL
A write must be written to all replica nodes in the cluster for the associated partition.A read returns the record only after all replicas have responded, while the operation fails if a single replica does not respond.
Note: This option provides the highest consistency and the lowest availability.
QUORUM
A write must be written on a quorum of replica nodes across all datacenters.
A read returns the record after a quorum of replicas from all datacenters has replied.
Note: This option provides a balance between strong consistency and tolerance to a small number of failures.
ONE
A write must be written to at least one replica node.
A read returns the record after the response ...