GraphQL in Kotlin. Building Modern APIs

The book "GraphQL in Kotlin" is a comprehensive practical guide to building modern, flexible, and high-performance APIs using the Kotlin language and GraphQL technology. Unlike REST, GraphQL allows clients to request only the data they actually need, which significantly simplifies the development of mobile and web applications, reduces the amount of transmitted data, and speeds up service performance.

This book is written for developers who are already familiar with the basics of Kotlin and want to master a modern approach to building APIs. You will learn how to design a data schema, configure resolvers, handle errors, and implement real business logic. Special attention is given to integrating GraphQL with popular frameworks such as Spring Boot and Ktor.

What you will learn from the book:

• GraphQL basics: types, queries, mutations, and subscriptions.
• Designing efficient schemas and working with the data graph.
• Integrating GraphQL with Spring Boot: setup, configuration, middleware.
• Implementing authentication and authorization at the GraphQL level.
• Query optimization: solving the N+1 problem, batching, and caching.
• Testing GraphQL endpoints: unit, integration, and e2e tests.
• Working with subscriptions for real-time functionality.
• Advanced techniques: federation, directives, custom scalars.
• Deploying and monitoring a GraphQL server in production.

The book contains numerous practical examples, ready-to-use code snippets, and step-by-step instructions. You will not just study theory — you will immediately apply your knowledge in practice by building a full-fledged API for an online store, social network, or content management system.

Who this book is for:

• Backend developers using Kotlin and Java who want to learn GraphQL.
• Full-stack developers looking to improve frontend-backend interaction.
• Architects and team leads planning to adopt GraphQL in existing projects.
• Anyone interested in modern API building technologies.

By the end of the book, you will be able to independently design, develop, and maintain a GraphQL server in Kotlin, ready for high loads. You will understand how to avoid common mistakes and make your API fast, secure, and convenient for clients.

Start your journey into the world of GraphQL with Kotlin — a language that combines conciseness, expressiveness, and full compatibility with the Java ecosystem. This book will be your reliable guide from the first queries to industrial use.