Summary  
This chapter introduces NoSQL databases as non-relational data stores with flexible schemas and horizontal scalability, and outlines their main types—including document, key-value, column-family, and graph databases.

General domain of usage  
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**NoSQL**, which stands for **"Not Only SQL"**, refers to a broad category of database management systems that are designed to handle a wide variety of data models, particularly **non-relational** or **semi-structured data**.    
 Unlike traditional relational databases, which use structured query language (SQL) to define and manipulate data, NoSQL databases offer a more flexible schema design and are optimized for large-scale data storage and retrieval.

### Why NoSQL?

NoSQL databases are designed to handle:

- **Unstructured or Semi-structured Data**: data that does not fit neatly into tables, rows, and columns, such as JSON documents, key-value pairs, graphs, and wide-column stores;
- **High Scalability**: horizontal scaling, where databases can distribute data across **many servers**, making it easier to handle large volumes of data and high transaction loads;
- **Flexibility**: dynamic schemas that allow for the addition of new fields without the need for database downtime or complex schema migrations.


Which of the following is NOT a type of NoSQL database?

Explore advanced SQL concepts essential for backend development. Learn about ACID transaction properties, query optimization, indexing strategies, window functions, and triggers, and understand how these features help build efficient and reliable database systems used in large-scale backend applications.

NoSQL

Why NoSQL?

NoSQL database types