Handy API Extension Patterns : How to Evolve Message Formats Without Breaking Everything

Change is inevitable. This short guide shows you how to evolve your API messages safely, without breaking existing clients or losing control of your schema.

In this compact and practical guide, Mike Amundsen shares a proven design pattern for safely evolving API response payloads without triggering downstream failures. Starting with a clear look at strong, weak, and "mild" typing styles, the book introduces a resilient approach using structured extensions and runtime accessors that allow APIs to grow gracefully over time.

Whether you're maintaining legacy services or building future-facing systems, this book gives you the tools to design messages that are stable, flexible, and ready for change.