A REST API allows communication between client and server using HTTP methods like GET, POST, PUT, DELETE. This guide walks you through the complete backend flow with real-world examples.
APIs are the backbone of modern software. Every app you use — from social media to banking — relies on APIs to exchange data between the frontend and backend. Understanding how they work is essential for any developer.
What is a REST API?
REST stands for Representational State Transfer. It is an architectural style that defines a set of constraints for creating web services. RESTful APIs use HTTP protocols and standard methods to perform operations on resources.
The beauty of REST is its simplicity and universality. Any client that can make HTTP requests can communicate with a REST API, regardless of programming language or platform.
Request Lifecycle
Client → Server → Route → Controller → Database → Response. This is the journey every API request takes. Understanding each step helps you build more robust and efficient systems.
When a client sends a request, the server receives it, matches it to a route, passes it to the appropriate controller, which performs any necessary business logic and database operations, and finally sends back a response.
Routing and Controllers
Routes define endpoints. Controllers handle logic. This separation keeps code clean and maintainable. Routes are like a table of contents, telling the server where to send each request.
Controllers contain the business logic for each endpoint. They validate input, interact with databases or external services, and format the response. Keeping controllers focused on a single responsibility makes them easier to test and maintain.
Database Interaction
Controllers interact with databases using queries or ORM tools. ORMs like Prisma, Sequelize, or Mongoose provide a higher-level interface for database operations, reducing boilerplate and improving type safety.
Understanding raw SQL alongside ORM usage gives you the flexibility to optimize queries when needed and debug issues that ORMs might obscure.
Real World Flow
Login request: client sends credentials → server validates → JWT generated → response sent. This real-world example shows how all the pieces come together in a practical authentication flow.
Security considerations like password hashing, token expiration, and rate limiting are crucial parts of any production API. The flow might look simple, but each step requires careful implementation.
