Databases – Key Value Databases

title: Key Value Databases

Key Value Databases

A key-value database, or key-value store, is a type of NoSQL database that uses a key/value storage. This means that the data stored in the database is a collection of key-value pairs.

This type of data structure is used on many programming languages. Key-value pairs are commonly known as associative arrays, dictionaries or hash. For example, consider a dictionary of phone numbers:


The Key

The key in a key-value pair must be unique. Having a unique identifier will allow you to access the value associated with a given key.

In theory, the key can be anything you want. A key can be a string, a binary sequence, an image, among others. However, some databases may impose limitations on the type of keys that can be used.

Here are some recommendations:

  • Keys should follow a convention in order to have consistency. Keys in a phone numbers dictionary should always be names, and not a combination of names, e-mail addresses and numbers.
  • Keys should not be too long, or you might have performance issues.
  • Keys should not be too short, or you might have readability issues.

The Value

The value in a key-value store can be anything you want. This includes strings, numbers, code, an image, a list, or even another key-value pair. Some databases allow you to restrict the data type that can be stored.

Use Cases

Key-value databases can be used on multiple scenarios. Here is a list of the most common applications:

  • Telecom directories.
  • User profiles and session information.
  • Shopping cart contents.
  • Product details or reviews.
  • Internet Protocol (IP) forwarding tables.
  • Services health status or configuration.


Here are some examples of databases that use the key-value approach:

More Information:

Key-Value database is a simple database that uses a map or a dictionary as the fundamental data model where each key is associated with one and only one value in a collection and is the most flexible type of NoSQL database.

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