What are the key principles of the REST architectural style?

The key principles of the REST (Representational State Transfer) architectural style include:

• Client-server architecture: separation of concerns between the client and the server.
• Stateless: each request from the client to the server must contain all the information needed to process the request, and the server does not store any state between requests.
• Caching: responses can be explicitly or implicitly marked as cacheable or non-cacheable to improve performance.
• Uniform interface: simplifies and decouples architecture, includes the use of standard HTTP methods (GET, POST, PUT, DELETE) and resource identifiers (URI).
• Layered system: architecture can consist of multiple layers, which are not visible to each other.
• Code on demand (optional): the server can transfer executable code to the client to extend functionality.

These principles help create scalable, flexible, and easily maintainable web services.