Which type of nonrelational database employs a simple key-value method for data storage?

The type of nonrelational database that employs a simple key-value method for data storage is the key-value pair database. This database design is characterized by its use of a dictionary or map structure, where each key is unique and directly corresponds to a single value. This simplicity allows for efficient data retrieval, as you can quickly access a value based on its associated key.

Key-value pair databases are particularly useful for applications that require high-speed reads and writes or when data is largely unstructured. They are often used in scenarios where the data does not need complex querying or relationships, making them a popular choice for caching, session management, and storing user preferences.

The other types of databases mentioned serve different purposes: document storage databases manage semi-structured documents, graph databases focus on the relationships between data points often used in networking or social applications, and object storage manages large amounts of unstructured data as objects rather than a particular data model. Each serves specific use cases in data management but does not follow the straightforward key-value approach typical of key-value pair databases.