Key–value database

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.

[citation needed] 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 maintain data in memory (RAM), while others employ solid-state drives or rotating disks.

[2] The Unix system provides dbm (database manager), which is a 1979 library originally written by Ken Thompson.

Although dbm precedes the concept of a NoSQL and is rarely mentioned in modern discourse, it is used by many pieces of software.