Apache Cassandra is a distributed, open source, highly-scalable NoSQL database system. It was initially released in 2008 by Facebook and has since been adopted by many organizations to store large amounts of data in a highly available and reliable manner. Cassandra is designed to be fault tolerant and can easily scale as the volume of data increases.
Cassandra stores its data using a partitioned row store with tunable consistency. It utilizes a master-less architecture in which each node serves as both the client and server, allowing for rapid scalability with no single point of failure. This allows for the system to continue functioning even if multiple nodes fail at once. In addition, Cassandra provides built-in support for replication which helps ensure that data remains consistent across all nodes in the cluster.
Cassandra also provides several features that make it useful for applications requiring high availability such as online transactions or real-time analytics. It supports tunable consistency levels which allows developers to configure consistency on a per-query basis, enabling strong read/write consistency when needed while still providing low latency queries when possible. Additionally, Cassandra provides built-in support for sharding which enables it to distribute workloads across multiple physical machines while still providing linear scalability as the number of nodes grows.
Overall, Apache Cassandra is an excellent choice for applications that need scalability and high availability without sacrificing performance or reliability. Its masterless architecture makes it easy to scale up or down quickly without having to worry about managing individual nodes or maintaining complex replication configurations. Additionally, its tunable consistency levels provide flexibility when defining query behavior while its built-in sharding capabilities make it easy to distribute workloads across multiple physical machines without having to manually configure replication or partitioning settings manually.