A key–value database, or key–value store, is a data storage paradigm designed for storing, retrieving, and managing associative arrays, and 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.
Key–value databases work in a very different fashion from the better known relational databases (RDB). RDBs predefine the data structure in the database as a series of tables containing fields with well defined data types. Exposing the data types to the database program allows it to apply a number of optimizations. In contrast, key–value systems treat the data as a single opaque collection, which may have different fields for every record. This offers considerable flexibility and more closely follows modern concepts like object-oriented programming. Because optional values are not represented by placeholders or input parameters, as in most RDBs, key–value databases often use far less memory to store the same data, which can lead to large performance gains in certain workloads.
Performance, a lack of standardization and other issues 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, are also key–value databases internally, adding the concept of the relationships (pointers) between records as a first class data type.
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.
Every entity (record) is a set of key–value pairs. A key has multiple components, specified as an ordered list.
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An embedded database system is a database management system (DBMS) which is tightly integrated with an application software; it is embedded in the application. It is a broad technology category that includes: database systems with differing application programming interfaces (SQL as well as proprietary, native APIs) database architectures (client-server and in-process) storage modes (on-disk, in-memory, and combined) database models (relational, object-oriented, entity–attribute–value model, network/CODASYL) target markets The term embedded database can be confusing because only a small subset of embedded database products are used in real-time embedded systems such as telecommunications switches and consumer electronics.
Aerospike Database is a flash memory and in-memory open source distributed key value NoSQL database management system, marketed by the company also named Aerospike. Aerospike was first known as Citrusleaf. In August 2012, the company - which had been providing its database since 2010 - rebranded both the company and software name to Aerospike. The name "Aerospike" is derived from the aerospike engine, a type of rocket nozzle that is able to maintain its output efficiency over a large range of altitudes, and is intended to refer to the software's ability to scale up.
In the field of database design, a multi-model database is a database management system designed to support multiple data models against a single, integrated backend. In contrast, most database management systems are organized around a single data model that determines how data can be organized, stored, and manipulated. Document, graph, relational, and key–value models are examples of data models that may be supported by a multi-model database. The relational data model became popular after its publication by Edgar F.
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