Key-value databases, also called key-value stores, are often considered the simplest type of NoSQL databases. Each unique identifier is stored as a key with its associated value. The value can be any sort of byte array, data structure, or binary large object (BLOB), and works well for storing enormous amounts of data. Windows Explorer and Apple Finder are both key-value databases.
Key-value stores are not considered suitable for applications requiring frequent updates or for complex queries involving specific data values, or multiple unique keys and relationships between them.
Other Definitions of Key-Value Store Include:
A database implementing a hash table to store unique keys along with the pointers to the corresponding data values.
“An in-memory data store used as a database, cache and message broker.” (Redis)
The most flexible type of NoSQL database and an alternative to traditional relational databases.
“Collection of paired identifiers, called ‘keys,’ and facts, called ‘values'”. (Forbes).
“Databases that store key and value data in lookup.” (IBM).
Database that stores data in only two columns (“key” and “value”), including simple (dates, numbers, codes) and complex information (unformatted text, video, music, documents, photos) within the key and value columns respectively.