Key–value database
File:BabbageKeyValueCard.tiff A key-value database, or key-value store, is a data storage paradigm designed for storing, retrieving, and managing associative arrays, a data structure more commonly known today as a dictionary or hash table. Dictionaries contain a collection of objects, or records, which in turn have many different fields within them, each containing data. These records are stored and retrieved using a key that uniquely identifies the record, and is used to find the data within the database.[1][2]
Performance, a lack of standardization and other issues have limited key-value systems to niche uses for many years, but the rapid move to cloud computing after 2010 has led to a renaissance as part of the broader NoSQL movement. Some graph databases, such as ArangoDB,[3] are also key–value databases internally, adding the concept of the relationships (pointers) between records as a first class data type.
Types and examples
Key-value databases can use consistency models ranging from eventual consistency to serializability. Some support ordering of keys.
Some maintain data in memory (RAM), while others employ solid-state drives or rotating disks.[1]
Every entity (record) is a set of key–value pairs. A key has multiple components, specified as an ordered list. The major key identifies the record and consists of the leading components of the key. The subsequent components are called minor keys. This organization is similar to a directory path specification in a file system (e.g., /Major/minor1/minor2/). The “value” part of the key–value pair is simply an uninterpreted string of bytes of arbitrary length.[4]
The Unix system provides dbm (database manager), which is a 1979 library originally written by Ken Thompson. It is also ported to Microsoft Windows, provided through programming languages such as Perl for Win32. The dbm manages associative arrays of arbitrary data by use of a single key (a primary key). Modern implementations include sdbm, GNU dbm, and Berkeley DB. Although dbm precedes the concept of a NoSQL and is rarely mentioned in modern discourse, it is used by many pieces of software.
A more recent example of a key-value database is RocksDB which is used as storage engine for other database management systems such as ArangoDB. Other examples include Aerospike (database), Amazon DynamoDB, Memcached, Redis, and ScyllaDB.
See also
- Big data
- Data analysis
- Distributed data store
- Document-oriented database
- Multi-model database
- Tuple space
- Ordered Key-Value Store
- Name–value pair
References
- ↑ 1.0 1.1 Corbellini, Alejandro; Mateos, Cristian; Zunino, Alejandro; Godoy, Daniela; Schiaffino, Silvia (2017-01-01). "Persisting big-data: The NoSQL landscape". Information Systems 63: 1–23. doi:10.1016/j.is.2016.07.009. ISSN 0306-4379. https://www.sciencedirect.com/science/article/pii/S0306437916303210. Retrieved 2025-05-25.
- ↑ Hecht, Robin; Jablonski, Stefan (2011). "NoSQL evaluation: A use case oriented survey". 2011 International Conference on Cloud and Service Computing. pp. 336–341. doi:10.1109/CSC.2011.6138544.
- ↑ "Storage Engines". https://www.arangodb.com/docs/stable/architecture-storage-engines.html.
- ↑ Oracle NoSQL Database.
 |  |
