API Development in JavaScript (Node.js)

This book is a practical guide to building modern APIs with Node.js. It will take you from the basics of web service design to deploying a finished product in the cloud. You will learn not just to write code, but to design reliable, scalable, and secure APIs that will serve as the foundation for web applications, mobile clients, and microservice architecture.

The book is built around a real project — you will create a full-fledged API for an online store. Each chapter adds new functionality: from basic CRUD operations to authentication, pagination, caching, and error handling. You will learn how to choose between REST and GraphQL, design endpoints, work with databases (MongoDB and PostgreSQL), optimize queries, and protect your application from attacks.

Special attention is paid to practical aspects:

• API design: RESTful architecture, versioning, HATEOAS
• Working with Express.js and Fastify — choosing the right framework for the task
• Authentication: JWT, OAuth 2.0, sessions, refresh tokens
• Data validation, error handling, logging
• API testing: unit tests, integration tests, load testing
• Documentation: Swagger/OpenAPI, automatic documentation generation
• Optimization: caching, connection pooling, rate limiting
• Deployment: Docker, CI/CD, monitoring, logging in production

The book is aimed at developers who are already familiar with the basics of JavaScript and want to delve into backend development. It will be useful both for beginner Node.js developers looking for a structured introduction to the topic, and for experienced programmers who want to systematize their knowledge and master modern approaches (microservices, event-driven architecture, serverless).

After reading, you will be able to independently design and develop APIs of any complexity level, understand which tools and patterns to apply in various scenarios, and most importantly, create code that is easy to maintain and scale. All examples are available in the repository and come with detailed comments.