Which of the following best describes the principle of state in REST APIs?

The principle of state in REST APIs is defined by the concept of statelessness, which means that each API call is independent of previous calls. This independence ensures that each request from a client to the server must contain all the information the server needs to fulfill that request. The server does not store any session data or context about the client between requests. This design simplifies the server architecture, as it does not have to keep track of client states, making the API scalable and easier to manage.

In contrast, the other options describe aspects that do not align with the core principle of REST. Maintaining session data is contrary to the statelessness principle since it would require the server to remember previous interactions. While authentication is often important for securing an API, it is not a defining characteristic of REST itself; APIs can be stateless while still requiring authentication. Lastly, the assertion that statelessness increases backend complexity is misleading, as one of the benefits of a stateless architecture is its ability to reduce complexity by allowing horizontal scaling of services without the need to maintain session data.