A database cache is supplementary to your primary database, either built into your database itself or as an additional layer. It exists to radically speed up read access to frequently-queried data and reduce pressure on the primary database, allowing you to scale while consuming fewer resources. Caches exist for both relational and non-relational databases. These solutions frequently use a key-value data structure.
Placing the data most frequently requested by users in fast-access memory or closer to the front-end allows you to serve up content much more quickly. As a result, it is particularly useful for applications where speed is key, such as real-time or location-based recommendation engines, mobile development, and web development.