What is meant by RESTful API and what characteristics does it have?

RESTful API is an architectural style for creating web services that uses the principles of REST (Representational State Transfer). The main features of RESTful API:

• Client-server architecture: clients and servers are separated, allowing independent development.

• Stateless: each request from the client to the server must contain all the information needed for processing; the server does not store state between requests.

• Cacheability: server responses should explicitly indicate whether they can be cached, improving performance.

• Uniform interface: use of standard HTTP methods (GET, POST, PUT, DELETE, etc.) for resource operations.

• Resource identification: resources are identified via URLs (e.g., /users/123).

• Layered system: architecture can have multiple layers (proxies, load balancers) that do not affect client-server interaction.

Example of a RESTful API request in C# using HttpClient:

using System.Net.Http;
using System.Threading.Tasks;

HttpClient client = new HttpClient();

// Get user with id=123
HttpResponseMessage response = await client.GetAsync("https://api.example.com/users/123");
string content = await response.Content.ReadAsStringAsync();

// content contains user data in JSON format

Thus, RESTful API is built around resources and standard HTTP operations, ensuring simplicity and scalability.