Which design pattern is used in API?

Several design patterns are commonly used when designing APIs to ensure they are scalable, maintainable, and user-friendly. Here are the key design patterns often used in API design:

1. REST (Representational State Transfer)

• Description: REST is a well-known design pattern that organizes APIs around resources (nouns like users, products, etc.) and uses standard HTTP methods (GET, POST, PUT, DELETE) for interactions.
• When to use: REST is ideal for APIs that need to be simple, stateless, and easily scalable. It provides a uniform interface for interactions.
• Example: A RESTful API for a book service might use endpoints like:
  • GET /books: Retrieves all books.
  • POST /books: Adds a new book.
  • DELETE /books/{id}: Deletes a book by ID.

2. GraphQL

• Description: A more flexible design pattern that allows clients to request exactly the data they need, reducing over-fetching and under-fetching of information.
• When to use: GraphQL is useful when you have complex relationships between resources and need to reduce the number of network calls.
• Example: A client can query both books and their authors in a single request:

  {
    books {
      title
      author {
        name
      }
    }
  }

3. Chain of Responsibility

• Description: This design pattern allows the handling of API requests to pass through a chain of handlers, with each handler responsible for processing or passing the request along.
• When to use: It is often used in middleware architecture (e.g., in Node.js or Express.js) to handle tasks like authentication, logging, and error handling.
• Example: A request passes through several middleware functions in an Express app, such as:
  • Authentication middleware.
  • Validation middleware.
  • Response middleware.

4. Command Pattern

• Description: This pattern encapsulates a request as an object, allowing for the separation of request execution from request creation.
• When to use: It’s useful when you need to implement complex business logic in your API.
• Example: In a task management API, different commands (CreateTask, UpdateTask) are represented as objects and executed independently.

5. Adapter Pattern

• Description: The Adapter Pattern is used to make different APIs compatible with a system without changing the core logic of the system.
• When to use: Useful for integrating third-party APIs or legacy systems with a new API structure.
• Example: Adapting data from a third-party payment API into your API’s format, ensuring seamless integration.

6. Facade Pattern

• Description: The Facade pattern provides a simplified interface to a complex system of APIs, making it easier for clients to interact with the system without worrying about the underlying complexity.
• When to use: When you have a complex set of services, such as microservices, and want to present a simpler interface to external clients.
• Example: A single endpoint in a REST API that aggregates data from multiple services (e.g., user data, order data, and payment data) into one response.

7. Proxy Pattern

• Description: In this pattern, a proxy object controls access to another object, which might be remote or require some preprocessing before returning data.
• When to use: Common in APIs where you want to control or cache access to external resources (e.g., rate limiting or lazy loading).
• Example: A proxy could be used to cache responses from an external API and reduce the number of calls.

8. Decorator Pattern

• Description: The decorator pattern allows you to dynamically add behaviors or responsibilities to objects (in this case, API requests).
• When to use: It is useful in scenarios where additional processing or logic needs to be added, such as logging, validation, or error handling.
• Example: Adding a logging decorator to track every API request and response for debugging purposes.

Conclusion

The choice of design pattern depends on your API’s goals and complexity. REST and GraphQL are architectural patterns used widely, while other patterns like Chain of Responsibility, Facade, and Proxy provide flexibility in handling different aspects of API functionality, from security to data aggregation.