In what cases are NoSQL databases used?

NoSQL databases are used in the following cases:

• When data has a non-relational structure, such as documents, graphs, key-value, or columnar data.
• For horizontal scaling and high performance with large volumes of data.
• When a flexible data schema is required, which can change frequently, without the need to rigidly define table structures.
• For processing large streams of data in real-time.
• In cases where high availability and fault tolerance are important.

Example: MongoDB (a document database) is often used to store JSON-like documents with a dynamic structure, which is convenient for web applications with changing data requirements.

Thus, NoSQL is suitable for projects with large, diverse, and rapidly changing data, where traditional relational databases may be less effective.