API Architecture: 11 Design Best Practices for REST APIs

REST APIs are a popular way of building web services that can communicate with different clients and platforms. They are based on the principles of Representational State Transfer (REST), which is an architectural style for designing networked applications. REST APIs use HTTP methods, such as GET, POST, PUT, and DELETE, to perform operations on resources, which are identified by Uniform Resource Identifiers (URIs).

However, designing a good REST API is not a trivial task. There are many aspects to consider, such as naming conventions, data formats, error handling, security, documentation, and more. Today, let’s look at 11 design best practices for REST APIs that can help you create more consistent, maintainable, and user-friendly web services.

1. Use Nouns for Resource Names

A resource is anything that can be named and manipulated by the API, such as a user, a product, or an order. Resource names should be nouns, not verbs, and should use plural forms to indicate collections of resources. For example, use /users instead of /user or /getUsers.

2. Use Sub-resources for Relationships

If a resource has a relationship with another resource, you can use sub-resources to represent the hierarchy. For example, if a user has multiple orders, you can use /users/{userId}/orders to access the orders of a specific user.

3. Use HTTP Methods for CRUD Operations

CRUD stands for Create, Read, Update, and Delete, which are the four basic operations that can be performed on a resource. You should use an appropriate HTTP method for each operation.

  • POST: Create a new resource or a sub-resource. For example, use POST /users to create a new user or POST /users/{userId}/orders to create a new order for a user.
  • GET: Read or retrieve a resource or a collection of resources. For example, use GET /users to get all users or GET /users/{userId} to get a specific user.
  • PUT: Update or replace a resource or a sub-resource. For example, use PUT /users/{userId} to update the details of a user or PUT /users/{userId}/orders/{orderId} to update the status of an order.
  • DELETE: Delete a resource or a sub-resource. For example, use DELETE /users/{userId} to delete a user or DELETE /users/{userId}/orders/{orderId} to delete an order.

4. Use Query Parameters for Filtering, Sorting, and Pagination

Query parameters are key-value pairs that are appended to the URI after a question mark (?). They can be used to modify the response of a GET request by applying filters, sorting criteria, or pagination limits. For example:

  • GET /users?role=admin: Get only the users who have the role of admin.
  • GET /products?sort=price&order=asc: Get the products sorted by price in ascending order.
  • GET /orders?page=2&size=10: Get the second page of orders with 10 orders per page.

5. Use Status Codes to Indicate the Outcome of a Request

Status codes are three-digit numbers that are returned by the server along with the response body. They indicate whether the request was successful or not and provide additional information about the result. You should use the standard HTTP status codes as much as possible.

  • 2xx: Success. The request was completed successfully, and the response body contains the expected data.
  • 3xx: Redirection. The request was redirected to another URI or requires further action from the client.
  • 4xx: Client error. The request was invalid or cannot be processed by the server due to some error on the client side.
  • 5xx: Server error. The request failed due to some error on the server side that is not related to the client.

6. Use Descriptive and Consistent Error Messages

Error messages are strings that are returned by the server in the response body when something goes wrong with a request. They should provide clear and helpful information about what caused the error and how to fix it if possible. You should also use a consistent format for your error messages, such as JSON or XML, and include relevant fields such as code, message, details, etc.

7. Use JSON or XML for Data Exchange

JSON and XML are two common formats for representing and exchanging data over the web. They are both human-readable and machine-parseable, and can support complex and nested structures. You should choose one of them as your default format for your REST API and stick to it throughout your service. You can also support both formats by using the Content-Type and Accept headers to indicate the format of the request and response bodies.

8. Use HTTPS for Security

HTTPS is a protocol that encrypts the communication between the client and the server using SSL/TLS certificates. It ensures that the data exchanged over the web is secure and confidential, and prevents unauthorised access, modification, or interception. You should use HTTPS for your REST API, especially if you are dealing with sensitive or personal data, such as passwords, credit card numbers, or health records.

9. Use Authentication and Authorisation for Access Control

Authentication and authorisation are two mechanisms that control who can access and use your REST API. Authentication verifies the identity of the client, while authorisation determines the level of access or permissions that the client has. There are many ways to implement authentication and authorisation for your REST API, such as basic authentication, token-based authentication, OAuth, etc. You should choose the one that suits your needs and requirements and apply it consistently across your service.

10. Use Documentation to Describe the REST API

Documentation is a written description of your REST API that explains its purpose, functionality, and usage. It should provide information about the resources, methods, parameters, formats, status codes, error messages, examples, and more. Documentation is essential for making your REST API understandable and usable by other developers or clients. You should use a tool or a framework to generate and maintain your documentation, such as Swagger or Postman.

11. Use Versioning to Manage Changes to the REST API

Versioning is a way of tracking and managing the changes that you make to your REST API over time. It allows you to introduce new features, fix bugs, or improve performance without breaking the existing functionality or compatibility of your service. You should use a versioning scheme for your REST API, such as semantic versioning or date-based versioning, and include it in the URI or the headers of your requests and responses.

11 Design Best Practices for REST APIs

We should all strive to make APIs a pleasure to use. Both, for consumers and our own fellow developers.

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