Which NoSQL database is open source and uses its own language?

• A. Cassandra
• B. MongoDB
• C. HBase
• D. CouchDB

Answer: (A)

Cassandra is an open-source NoSQL database that is designed to handle large amounts of data across many servers while providing high availability without a single point of failure. It uses its own query language called CQL (Cassandra Query Language), which is similar to SQL but tailored specifically for Cassandra's architecture.

This language allows users to interact with the data in a familiar manner if they are already accustomed to SQL, but it also accommodates the unique features of Cassandra, such as its ability to handle denormalized data models. The key features of Cassandra, including its scalability and resilience, are particularly beneficial for applications that require a distributed system with fault tolerance and heavy read/write capabilities.

While options like MongoDB, HBase, and CouchDB are also popular NoSQL databases, they utilize their own query languages or APIs, but they don't necessarily match the criteria of being specifically tailored like CQL in Cassandra.