The document provides an introduction and overview of NoSQL databases. It discusses:
- How NoSQL databases are non-relational and differ from traditional relational databases by not requiring fixed schemas and supporting horizontal scaling.
- Examples of different types of NoSQL databases like document stores, key-value stores, and graph databases.
- The CAP theorem and eventual consistency of NoSQL databases, which allow high availability and partitioning at the cost of strong consistency.
- How NoSQL databases are used by large companies to store rapidly growing unstructured and unpredictable data more efficiently than relational databases.