Can you explain RESTful principles and how they apply to API design?

[fastqa]

RESTful principles are a set of guidelines for designing networked applications. They rely on a stateless, client-server, cacheable communications protocol -- the HTTP protocol is commonly used.

Key Principles

• Stateless: Each request from client to server must contain all the information needed to understand and process the request.
• Client-Server: Separates the user interface concerns from the data storage concerns. Improves portability across multiple platforms.
• Cacheable: Responses must define themselves as cacheable or non-cacheable to prevent clients from reusing stale or inappropriate data.
• Uniform Interface: Simplifies and decouples the architecture, which enables each part to evolve independently.
• Layered System: Architecture is composed of hierarchical layers by constraining component behavior.