GraphQL in Kotlin: Building Modern APIs

This book is your guide to the world of building modern and flexible APIs using the Kotlin language and GraphQL technology. If you are tired of the rigid constraints of REST and want to give clients the ability to request exactly the data they need, this book is for you.

What is this book about?

We start with the basics: what GraphQL is, how it differs from REST and SOAP, and why Kotlin is the ideal language for its implementation. You will learn how to design your API schema, describe types, mutations, and subscriptions. Next, we dive into practice: from setting up a project on Ktor and Spring Boot to implementing complex queries with filtering, pagination, and error handling. Special attention is paid to performance — you will learn how to solve the N+1 query problem using DataLoader and batch data loading.

Who is this book for?

• For Kotlin developers who want to master a modern approach to building APIs.
• For Java developers transitioning to Kotlin and wanting to learn GraphQL.
• For backend engineers looking for an alternative to REST and wanting to increase the flexibility of their services.
• For team leads and architects evaluating GraphQL for new projects.

What will you learn?

• How to design and implement a GraphQL schema in Kotlin.
• How to integrate GraphQL with popular frameworks: Ktor, Spring Boot, http4k.
• How to work with mutations and real-time subscriptions.
• How to ensure security: authentication, authorization, query validation.
• How to test GraphQL endpoints and write integration tests.
• How to optimize performance and avoid common mistakes.
• How to use GraphQL in a microservice architecture (Federation, Apollo Federation).

Why should you read this book?

The book is written by a practicing developer with many years of experience. Each chapter contains ready-made code examples that can be immediately applied in your projects. You will gain not only theoretical knowledge but also real tools for solving everyday tasks. After reading, you will be able to confidently design and develop GraphQL APIs in Kotlin that are fast, secure, and convenient for clients.

What's inside?

• Step-by-step creation of a full-fledged GraphQL service from start to finish.
• Analysis of real-world cases and architectural decisions.
• Tips on choosing libraries and tools.
• Ready-made templates for a quick start.

This book will become a desktop guide for everyone who wants to harness the full power of GraphQL and the elegance of Kotlin to build modern web services. Whether you are just starting your journey or already have experience, you will find valuable knowledge and practical advice here.