What is a REST API?

A REST API (also known as RESTful API) is an application programming interface (API or web API) that conforms to the constraints of the REST architectural style and allows for interaction with RESTful web services. REST stands for Representational State Transfer and was created by computer scientist Roy Fielding.

A RESTful system consists of:

  • A client who requests the resources.
  • The server that provides the resources.

Architectural Constraints of RESTful APIs:

There are six architectural constraints that define any RESTful web service:

  1. Uniform Interface
  2. Stateless
  3. Cacheable
  4. Client-Server
  5. Layered System
  6. Code on Demand (optional)

Best Practices for REST API Design

1. REST APIs Must Accept and Respond with JSON

REST APIs should accept JSON for request payloads and also send responses in JSON. JSON has become the standard for data exchange and is supported by nearly all programming languages. Server-side technologies can easily decode JSON, and JavaScript offers built-in methods to work with JSON.

2. Use Nouns Instead of Verbs in Endpoint Paths

Avoid using verbs in endpoint paths. Instead, use nouns that represent the entity being retrieved or manipulated. This makes the API easier to understand and aligns with RESTful conventions.

Example:

  • Correct: /employees
  • Incorrect: /getEmployees

3. Name Collections with Plural Nouns

Use plural nouns to represent collections in your API endpoints. This makes the purpose of the endpoint clear.

Example:

  • GET /cars/123

4. Nest Resources for Hierarchical Objects

Group related endpoints to reflect hierarchical relationships between objects. This practice improves clarity, even if the database structure doesn’t reflect the hierarchy.

Example:

  • GET /employees/1/leave

5. Handle Errors Gracefully and Return Standard Error Codes

When errors occur, handle them gracefully and return HTTP response codes that describe the error. This helps API consumers understand what went wrong.

6. Allow Filtering, Sorting, and Pagination

Large datasets can overwhelm the system if returned all at once. Enable filtering, sorting, and pagination to improve performance and usability.

7. Maintain Good Security Practices

  • Use SSL/TLS for secure communication.
  • Ensure users can only access the data they are authorized to view.
  • Group user permissions into roles, ensuring no unnecessary access is granted.

8. Cache Data to Improve Performance

Implement caching to reduce database queries and improve response times. Cached data can be served directly from memory for faster results.

9. Version Your APIs

Maintain different versions of your API when making changes that could break existing clients.

Example:

  • /v1/employees
  • /v2/employees

10. Provide API Documentation

Comprehensive documentation helps clients understand and use the API effectively.

Good documentation should include:

  • Endpoints and their purposes.
  • Example requests and responses.
  • Code examples in different programming languages.
  • Error messages and their corresponding status codes.

A popular tool for documenting REST APIs is Swagger.

Example API Endpoints

Resource POST GET PUT DELETE
/employees Create a new employee(s) Retrieve all employees Bulk update of employees Remove all employees
/employees/1 Error Retrieve the details for employee 1 Update the details of employee 1 if it exists Remove employee 1
/employees/1/leave Create a new leave request for employee 1 Retrieve all leaves for employee 1 Bulk update of leaves for employee 1 Remove all leaves for employee 1

References and Resources