Which option describes a Key-Value Database?

• A. JSON.
• B. A document store with JSON only.
• C. A graph database.
• D. A database that stores data in key-value pairs.

Answer: (D)

Key-value stores organize data as simple pairs: a unique key that identifies an item and a value that holds the data for that key. This makes retrieval straightforward and fast because you look up the value directly by its key, with minimal or no querying over multiple fields. The model is flexible in what the value can be—strings, blobs, or serialized objects—so you can store various data types under each key. This design is particularly suited to use cases like caching, session data, or configuration settings, where quick, direct access by a known identifier matters most.

In the options given, JSON is a data format, not a database. A document store uses documents (often JSON) as the unit of storage and supports querying within documents, which is a broader model than pure key-value access. A graph database stores data as nodes and relationships to enable traversals and complex queries, which is a different paradigm from key-value pairing. The description that precisely matches a key-value database is a database that stores data in key-value pairs.