What is the main difference between RESTful and RPC architectural styles when designing APIs?

The main difference between RESTful and RPC architectural styles in API design lies in the approach to interaction and resource organization:

• RESTful API is resource-oriented. Each resource has a unique URL, and operations on resources are performed using standard HTTP methods (GET, POST, PUT, DELETE). REST uses the concepts of resource state and representation, making the API more unified and scalable.

• RPC (Remote Procedure Call) is procedure or function-oriented. The API is a set of methods that are called directly, often via POST requests specifying the method name and parameters. RPC is less standardized and may be less convenient for caching and scaling.

Example:

RESTful:

GET /users/123  # Get user with ID 123
POST /users     # Create a new user

RPC:

POST /api
{
  "method": "getUser",
  "params": {"id": 123}
}

REST is more focused on resources and their states, while RPC is focused on calling specific actions.