Table of Contents

Foreword xiii
Preface xvii
Acknowledgments xxv
About the Authors xxxi

Part I: Transformational Strategic Learning through Experimentation 1

Executive Summary 3

Chapter 1: Business Goals and Digital Transformation 7
Digital Transformation: What Is the Goal? 8
Why Software Goes Wrong 11
Your Enterprise and Conway's Law 18
(Re)Thinking Software Strategy 24
Are Monoliths Bad? 30
Are Microservices Good? 31
Don't Blame Agile 34
Getting Unstuck 36
Summary 37
References 38

Chapter 2: Essential Strategic Learning Tools 39
Making Decisions Early and Late, Right and Wrong 40
Culture and Teams 43
Modules First 51
Deployment Last 55
Everything in Between 57
Where Is Your Spaghetti and How Fast Does It Cook? 70
Strategic Architecture 70
Applying the Tools 72
Summary 75
References 75

Chapter 3: Events-First Experimentation and Discovery 77
Commands and Events 78
Rapid Learning with EventStorming 81
Applying the Tools 92
Summary 99
References 100

Part II: Driving Business Innovation 101

Executive Summary 103

Chapter 4: Reaching Domain-Driven Results 109
Domains and Subdomains 111
Summary 115
References 116

Chapter 5: Contextual Expertise 117
Bounded Context and Ubiquitous Language 117
Core Domain 121
Supporting Subdomains, Generic Subdomains, and Technical Mechanisms 123
Business Capabilities and Contexts 125
Not Too Big, Not Too Small 128
Summary 129
References 130

Chapter 6: Mapping, Failing, and Succeeding--Choose Two 131
Context Mapping 131
Topography Modeling 151
Ways to Fail and Succeed 154
Applying the Tools 158
Summary 163
References 164

Chapter 7: Modeling Domain Concepts 165
Entities 166
Value Objects 167
Aggregates 168
Domain Services 169
Functional Behavior 170
Applying the Tools 173
Summary 173
References 174

Part III: Events-First Architecture 175

Executive Summary 177

Chapter 8: Foundation Architecture 181
Architectural Styles, Patterns, and Decision Drivers 183
Quality Attributes 196
Applying the Tools 206
Summary 207
References 208

Chapter 9: Message- and Event-Driven Architectures 211
Message- and Event-Based REST 216
Event-Driven and Process Management 220
Event Sourcing 223
CQRS 227
Serverless and Function as a Service 229
Applying the Tools 231
Summary 231
References 232

Part IV: The Two Paths for Purposeful Architecture 233

Executive Summary 235
Chapter 10: Building Monoliths Like You Mean It 239
Historical Perspective 241
Right from the Start 244
Right from Wrong 253
Keeping It Right 264
Summary 265
References 266

Chapter 11: Monolith to Microservices Like a Boss 267
Mental Preparation with Resolve 267
Modular Monolith to Microservices 271
Big Ball of Mud Monolith to Microservices 275
Unplugging the Legacy Monolith 286
Summary 287
References 288

Chapter 12: Require Balance, Demand Strategy 289
Balance and Quality Attributes 289
Strategy and Purpose 291
Conclusion 297
References 298

Index 299

About the Author

Vaughn Vernon, a software developer with over 30 years of experience in a broad range of business domains, is a world-renowned expert in Domain-Driven Design (DDD) and champion of simplicity and Reactive systems. As a consultant and teacher of DDD and Reactive software development, he has helped thousands of developers transform brittle, stagnating, technology-driven systems into innovative, business-driven systems that deliver far more value. The visionary and Chief Architect behind the VLINGO/PLATFORM, he is author of Implementing Domain-Driven Design, Domain-Driven Design Distilled, and Reactive Messaging Patterns with the Actor Model, all published by Addison-Wesley.

Tomasz Jaskuła has 20 years of professional experience as a developer, software architect, team leader, trainer, and technical conference speaker. An IDDD Workshop trainer in both French and Polish, he founded Paris Domain-Driven Design and F# user groups. Jaskuła's company, Luteceo (luteceo.fr), spreads good software and architecture practices based on Domain-Driven Design and software craftsmanship. He previously worked for many companies in e-commerce, industry, insurance, and finance, gaining deep experience for creating software that delivers clear business value and competitive advantage.

Reviews

"Most books address either the business of software or the technical details of building software. Strategic Monoliths and Microservices provides a comprehensive approach to blending the needs of business and technology in an approachable way. It also dispels many of today's myths while offering practical guidance that any team or organization can apply immediately and with confidence."
--James Higginbotham, Executive API Consultant, Founder of LaunchAny, and author of Principles of Web API Design

"Digital Transformation cannot succeed as a 'grass roots' effort. Vaughn and Tomasz offer C-level execs a roadmap to software excellence that includes establishing the culture necessary to foster and sustain software innovation. Written with real-world understanding, Vaughn and Tomasz help the reader to appreciate that moving software development from a cost center to a profit center involves tradeoffs that need not sacrifice innovation. A must-read for decision makers."
--Tom Stockton, Principal Architect, MAXIMUS

"In this book, Vaughn Vernon and Tomasz Jaskuła use their extensive experience with DDD to present a comprehensive guide to using the many different aspects of DDD for modern systems development and modernization. It will be a valuable guide for many technical leaders who need to understand how to use DDD to its full potential."
--Eoin Woods, software architect and author

"There are common misconceptions and roots of failure around software engineering. One notable example is neglecting the rugged trek towards digital transformation. Such an endeavor comprises breakthrough innovations, failure culture, emphasis on the role of software architecture, as well as on the importance of efficient and effective inter-human communication. Fortunately, the authors offer the necessary help for  mastering all hurdles and challenges. What I like most about this book is the holistic view it provides to all stakeholders involved in digital transformation and innovation. Vaughn Vernon and Tomasz Jaskuła introduce a clear path to successful innovation projects. They provide insights, tools, proven best practices, and architecture styles both from the business and engineering viewpoint. Their book sheds light on the implications of digital transformation and how to deal with them successfully. This book deserves to become a must-read for practicing software engineers, executives, as well as senior managers. It will always serve me as a precious source of guidance and as a navigator whenever I am entering uncharted territories."
--Michael Stal, Certified Senior Software Architect, Siemens Technology

"Digital transformation is a much used but little understood concept. This book provides valuable insight into this topic and how to leverage your existing assets on the journey. Modern technical and social techniques are combined in the context of a single case study. Compelling reading for both business and technology practitioners."
--Murat Erder, co-author of Continuous Architecture in Practice (2021) and Continuous Architecture (2015)

"Packed with insightful recommendations for every executive leader seeking clarity on the distinction between when to strategically apply a monolith vs. microservice architectural approach for success. Highly encourage every CEO, CIO, CTO, and (S)VP of Software Development to start here with immersing themselves in Vaughn and Tomasz's succinct distillation of the advantages, disadvantages, and allowance for a hybrid combination, and then go become a visionary thought leader in their respective business domain."
--Scott P. Murphy, Principal Architect, Maximus, Inc.

"A 'must-read' for Enterprise leaders and architects who are planning for or executing a digital transformation! The book is a true guide for ensuring your enterprise software innovation program is successful."
--Chris Verlaine, DHL Express Global Aviation IT DevOps Director, Head of DHL Express Global Aviation IT Software Modernization Program

" Strategic Monoliths and Microservices is a great resource to connect business value to an evolvable enterprise architecture. I am impressed with how the authors use their deep understanding and experience to guide informed decisions on the modularization journey. Along the way every valuable tool and concept is explained and properly brought into context. Definitely a must-read for IT decision makers and architects. For me this book will be an inspiring reference and a constant reminder to seek the purpose in architecture. The Microservices discussion has reached a completely new maturity level."
--Christian Deger, Head of Architecture and Platform at RIO | The Logistics Flow, organizer of over 60 Microservices Meetups

"The choice of microservices or monoliths architecture goes far beyond technology. The culture, organization, and communication that exist within a company are all important factors that a CTO must consider carefully in order to successfully build digital systems. The authors explain this extremely well from various perspectives and based on very interesting examples."
--Olivier Ulmer, CTO, Groupe La Française

"Building a technology engine to move quickly, experiment, and learn is a competitive advantage in today's digital world. Will ' de-jour architecture' help with this endeavor? This amazing book by Vaughn and Tomasz fills a void in the market and re-focuses on the core objectives of software architecture: move fast, experiment, focus on the outcomes that bring value. A reader will come away better suited to decide whether microservices architecture and all the complexity with it is right for them."
--Christian Posta, Global Field CTO, Solo.io