Which type of storage is accessed via an application program interface (API) and is not linked to a compute node?

The storage type that is accessed via an application program interface (API) and is not tied directly to a compute node is object storage. Object storage allows for the storage of large amounts of unstructured data and is designed to handle data in the form of objects, which include the data itself, metadata, and a unique identifier.

One of the distinguishing features of object storage is its ability to be accessed over the internet using APIs, which simplifies integration with applications and services. This enables developers to easily interact with the storage layer without the need to manage physical hardware or worry about the underlying infrastructure. As such, it can scale independently of compute resources, providing flexibility and efficiency in data management.

In contrast, other types of storage like direct attached, file, and block storage are typically associated with a compute resource. Direct attached storage is physically connected to a server and is not accessible over a network, while file and block storage typically involve relationships with specific compute nodes or require mounting, making them tightly coupled to those nodes. Hence, those options do not fulfill the criteria specified in the question.