What is the role of partition keys in Cassandra?

Partition keys play a crucial role in distributing data across a Cassandra cluster. They determine how data is hashed and where it is stored within the nodes of the cluster. When a partition key is defined for a table, Cassandra uses a consistent hashing algorithm to map the key to a particular token, which corresponds to a node in the cluster. This mechanism ensures that data is evenly distributed, promoting scalability and performance as data grows.

By distributing data using partition keys, Cassandra achieves efficient data retrieval and load balancing across its nodes. This allows for quick access to data and helps maintain high availability, as different nodes can process requests without overloading a single node.

This functionality is distinct from creating secondary indexes, defining data relationships, or controlling user access, which fulfill different roles in the database architecture.