There are several features that make Cassandra a desirable data store. Some of its more intrinsic features may not be overtly apparent to application developers and end users. But their ability to abstract complexity and provide performance ultimately aims to improve the experience on the application side. Understanding these features is paramount to knowing when Cassandra can be a good fit on the backend.
In Cassandra, multiple copies of the data are stored on multiple nodes. This design allows the cluster (and the applications that it serves) to continue to function in the event of a loss of one or more nodes. This feature allows Cassandra to remain available during maintenance windows and even upgrades.