Strategic Monoliths and Microservices

Vaughn Vernon is a champion of simplifying software architecture and development, with an emphasis on reactive methods. He has a unique ability to teach and lead with Domain-Driven Design using lightweight tools to unveil unimagined value. He helps organizations achieve competitive advantages using enduring tools such as architectures, patterns, and approaches, and through partnerships between business stakeholders and software developers.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.

"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

• Foreword xiiiPreface xviiAcknowledgments xxvAbout 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