Cassandra Practice Test 2026 - Free Practice Questions and Study Guide

The primary key in a data model serves as the unique identifier for each record within a dataset. It ensures that no two records can share the same value for this attribute, thereby maintaining the integrity of the data. In the context of Cassandra, the primary key consists of one or more columns that together guarantee uniqueness across the table.

While clustering keys contribute to how data is organized within the partition defined by the primary key, they do not ensure uniqueness on their own. Instead, they help to determine the order of rows within a partition. Secondary keys are utilized for querying data efficiently but do not establish primary-level uniqueness. Composite keys, which combine multiple attributes into a single key, may imply uniqueness as part of a broader primary key structure but do not exist on their own as unique identifiers.

Thus, the primary key stands out as the paramount element in defining uniqueness in the data model, making it the correct choice.