Why is horizontal scalability important for Cassandra?

Horizontal scalability is essential for Cassandra because it ensures that performance improves as more nodes are added to the database cluster. This characteristic allows organizations to effectively handle an increasing amount of data and user requests without a significant degradation in performance. As the workload grows, additional nodes can be integrated into the cluster. This not only enhances throughput but also provides redundancy and fault tolerance, ensuring that the system maintains high availability.

The ability to scale out by adding more hardware rather than upgrading the existing machines (a process known as vertical scaling) allows for seamless growth in infrastructure. This is critical for applications that demand constant performance, especially in scenarios with large volumes of transactions or high read/write activities. Thus, horizontal scalability directly supports the fundamental needs of modern distributed applications that rely on Cassandra.