The API-first development is one of the hottest technical topics nowadays, since many companies started to realize that API serves as a multiplicator to their opportunities—but it also amplifies the design mistakes as well.

This book is written to share the expertise and describe the best practices in designing and developing APIs. In Section I, we'll discuss the API architecture as a concept: how to build the hierarchy properly, from high-level planning down to final interfaces. Section II is dedicated to expanding existing APIs in a backwards-compatible manner. Finally, in Section III we will talk about the API as a product.

Illustration & inspiration: art.mari.ka.

You might download ‘The API’ in PDF, EPUB, or read it online.

Table of Contents

This book is distributed under the Creative Commons Attribution-NonCommercial 4.0 International licence.

Source code available at

About the Author

Sergey Konstantinov has been working with APIs for more than a decade. He started his career as a software engineer in the Maps API division at Yandex and eventually became the head of the service, being responsible for both technical architecture and product management.

During this tenure, Sergey got a unique experience in building world-class APIs with a daily audience of tens of millions, planning roadmaps for such a service, and giving numerous public speeches. He also worked for a year and a half as a member of the W3C Technical Architecture Group.

After nine years in Maps, Sergey switched to technical-lead roles in other departments and companies, leading integration efforts and being responsible for the technical architecture of entire business units. Today, Sergey lives in Tallinn, Estonia, and works as a staff software engineer at Bolt.

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