Proven Patterns for Designing Evolvable High-Quality APIs--For Any Domain, Technology, or Platform

APIs enable breakthrough innovation and digital transformation in organizations and ecosystems of all kinds. To create user-friendly, reliable and well-performing APIs, architects, designers, and developers need expert design guidance. This practical guide cuts through the complexity of API conversations and their message contents, introducing comprehensive guidelines and heuristics for designing APIs sustainably and specifying them clearly, for whatever technologies or platforms you use.

In Patterns for API Design: Simplifying Integration with Loosely Coupled Message Exchanges, five expert architects and developers cover the entire API lifecycle, from launching projects and establishing goals through defining requirements, elaborating designs, planning evolution, and creating useful documentation. They crystallize the collective knowledge of many practitioners into 44 API design patterns, consistently explained with context, pros and cons, conceptual solutions, and concrete examples. To make their pattern language accessible, they present a domain model, a running case study, decision narratives with pattern selection options and criteria, and walkthroughs of real-world projects applying the patterns in two different industries.

• Identify and overcome API design challenges with patterns
• Size your endpoint types and operations adequately
• Design request and response messages and their representations
• Refine your message design for quality
• Plan to evolve your APIs
• Document and communicate your API contracts
• Combine patterns to solve real-world problems and make the right tradeoffs

"This book provides a healthy mix of theory and practice, containing numerous nuggets of deep advice but never losing the big picture . . . grounded in real-world experience and documented with academic rigor applied and practitioner community feedback incorporated. I am confident that [it] will serve the community well, today and tomorrow."

--Prof. Dr. Dr. h. c. Frank Leymann, Managing Director, Institute of Architecture of Application Systems, University of Stuttgart

Table of Contents

Part 1: Foundations and Narratives

Chapter 1: Application Programming Interface (API) Fundamentals

Chapter 2: Lakeside Mutual Case Study

Chapter 3: API Decision Narratives

Part 2: The Patterns

Chapter 4: Pattern Language Introduction

Chapter 5: Define Endpoint Types and Operations

Chapter 6: Design Request and Response Message Representations

Chapter 7: Refine Message Design for Quality

Chapter 8: Evolve APIs

Chapter 9: Document and Communicate API Contracts

Part 3: Our Patterns in Action (Now and Then)

Chapter 10: Real-World Pattern Stories

Chapter 11: Conclusion

Appendix A: Endpoint Identification and Pattern Selection Guides

Appendix B: Implementation of the Lakeside Mutual Case

Appendix C: Microservice Domain-Specific Language (MDSL)

About the Author

Olaf Zimmermann is professor of software architecture at the Institute for Software at Eastern Switzerland University of Applied Sciences, Distinguished IT Architect at The Open Group, and co-editor of IEEE Software's Insights column. 

Mirko Stocker is professor of software engineering at Eastern Switzerland University of Applied Sciences, specializing on Web development and cloud solutions. 

Daniel Lübke is an independent coding and consulting architect who specializes in business process automation and digitization projects. 

Uwe Zdun is professor of software architecture at the University of Vienna, focusing on distributed systems engineering, DevOps, patterns, modeling, and empirical software engineering. 

Cesare Pautasso is a professor at the Università della Svizzera Italiana, where he leads the Architecture, Design, and Web Information Systems Engineering research group. The authors are active community members participating in pattern writer's workshops, shepherding other authors, serving on program committees, and chairing conferences.