What NoSQL databases have you worked with? What is a NoSQL database?

NoSQL databases are a type of database management systems that do not use the traditional relational model with tables and SQL queries. They are designed for storing and processing large volumes of data with high speed and flexibility, often in distributed systems.

Main types of NoSQL databases:

• Document (e.g., MongoDB, CouchDB) — store data in JSON-like document formats.
• Key-Value (e.g., Redis, Riak) — data is stored as key-value pairs.
• Column-Oriented (e.g., Cassandra, HBase) — optimized for storing and processing large amounts of data by columns.
• Graph (e.g., Neo4j) — designed for storing and analyzing graphs and relationships.

Among the NoSQL databases I have worked with are MongoDB and Redis. I used MongoDB for storing dynamic data structures where the schema can change frequently, and Redis for caching and quick data access in memory.