Can you list the types of databases you've worked with and explain their features?

I have worked with different types of databases, each with its own features:

• Relational databases (e.g., PostgreSQL, MySQL): use tables with a fixed schema, support SQL queries, transactions, and relationships between tables. Good for structured data and complex queries.

• Document-oriented databases (e.g., MongoDB): store data in JSON-like documents, flexible schema, convenient for unstructured or semi-structured data.

• Key-value (e.g., Redis): very fast access by key, used for caching and session storage.

• Columnar databases (e.g., Apache Cassandra): optimized for storing and processing large volumes of data, suitable for analytics and distributed systems.

The choice of database depends on the task: if you need strict structure and complex relationships — relational; if flexibility and scalability — NoSQL.