Apache Cassandra

Apache Cassandra is a distributed, wide-column database designed for handling large volumes of writes across many commodity servers with no single point of failure. Avinash Lakshman and Prashant Malik built it at Facebook to power the inbox search feature, and Facebook open-sourced it in 2008. It became an Apache top-level project in February 2010.

The current stable release is Cassandra 5.0. Every node in a Cassandra cluster is equal — there is no primary node, so there is no single point of failure and no read/write bottleneck. The database uses tunable consistency, allowing operators to choose per-query how many replicas must acknowledge a read or write — trading consistency against latency depending on the use case. Cassandra Query Language (CQL) provides a SQL-like interface for defining schemas and querying data. Version 5.0 introduced Storage-Attached Indexes (SAI) and vector search capabilities.

The official documentation covers architecture, data modeling, and operations. The source code is on GitHub under the Apache 2.0 license.