Apache Cassandra is an open-source, distributed NoSQL database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure. It was originally developed at Facebook to power their Inbox Search feature and later became an Apache Software Foundation project. Cassandra is widely recognized for its ability to scale, perform, and offer continuous uptime, making it a popular choice for businesses that require reliability and scalability, such as social media platforms, real-time big data analytics, and more. Cassandra's data model is based on a partitioned row store with tunable consistency. Rows are organized into tables; the first component of a table's primary key is the partition key; within a partition, rows are clustered by the remaining columns of the key. This design allows for flexible schema design and efficient data retrieval. Cassandra's architecture is peer-to-peer, which differs from a master-slave model. Each node in the cluster communicates with every other node, avoiding bottlenecks and single points of failure. Data is distributed across the cluster, but there is no master as every node can serve any request. Cassandra employs a mechanism called eventual consistency to provide both high availability and partition tolerance, with tunable consistency levels to manage the trade-off between read and write consistency.