GraphQL on Kotlin: Building Modern APIs

The book "GraphQL on Kotlin" is a comprehensive guide to building modern, flexible, and high-performance APIs. If you are already familiar with the basics of Kotlin and want to master one of the most in-demand approaches to backend development, this book will be your reliable assistant.

What is this book about?

The book systematically covers all aspects of working with GraphQL in the Kotlin ecosystem. You will start with the basics: what GraphQL is, how it differs from REST, and what problem it solves. Then you will move on to practical schema design, learning to describe types, queries, mutations, and subscriptions. Special attention is given to integration with popular frameworks such as Ktor and Spring Boot, as well as working with databases via Exposed or Room.

You will learn how to:

• Design strictly typed GraphQL schemas using Kotlin features (data classes, sealed classes, extension functions).
• Create efficient resolvers and optimize data loading using the DataLoader pattern.
• Implement authentication and authorization at the query level.
• Handle errors and exceptions, returning clear messages to the client.
• Set up subscriptions for real-time data (WebSocket).
• Write tests for GraphQL endpoints and document APIs using GraphQL Playground or GraphiQL.

Who is this book for?

• Kotlin backend developers who want to master a modern approach to building APIs.
• Developers familiar with REST but looking to learn a more flexible alternative.
• Students and professionals seeking to improve their skills and add a GraphQL project to their portfolio.
• Teams planning to migrate from REST to GraphQL or implement it in a new project.

What will you learn?

After reading this book, you will be able to independently design and deploy GraphQL servers on Kotlin. You will understand how to avoid common mistakes (N+1 problem, excessive data loading, inefficient resolvers) and how to build a scalable architecture. The book contains numerous code examples ready for use in real projects, as well as practical tips for performance optimization.

Start building APIs that give clients exactly the data they need — without excess and without missing anything. "GraphQL on Kotlin" is your guide to the world of modern backend development.