NoSQL

NoSQL ("not only SQL") refers to databases that store data in models other than relational tables. They are designed for flexible or changing data structures, very large volumes of data and easy horizontal scaling across many servers.

The main types are document databases (MongoDB, which stores JSON-like documents), key-value stores (Redis, DynamoDB), wide-column stores (Cassandra) and graph databases (Neo4j). Many NoSQL databases trade some consistency guarantees for availability and speed, and schemas are often defined by the application rather than the database.