The Structure of This Book

We changed the structure from the first edition to more clearly delineate the two main topics: the engineering practices for evolving software systems and the structural approaches that make it easier.

In Part I, we define the various mechanisms and engineering practices that teams can use to implement the goals of evolutionary architecture, including techniques, tools, categories, and other information readers need to understand this topic.

Software architecture also involves structural design, and some design decisions make evolution (and governance) easier. We cover this in Part II, which also includes coverage of architecture styles as well as design principles around coupling, reuse, and other pertinent structural considerations.

Virtually nothing in software architecture exists in isolation; many principles and practices in evolutionary architecture involve the holistic entanglement of many parts of the software development process, which we cover in Part III.

Case Studies and PenultimateWidgets

We highlight a number of case studies in this book. All four authors were (and some still are) consultants while working on the material in this book, and we used our real-world experience to derive many of the case studies that appear here. While we can’t divulge the details for particular clients, we wanted to provide some relevant examples to make the topic less abstract. Thus, we adopted the idea of a surrogate company, PenultimateWidgets, as the “host” for all our case studies.

In the second edition, we also solicited case studies from our colleagues, which further highlight examples of applying the techniques we discuss. Throughout the book, each case study appears as one from PenultimateWidgets, but each comes from a real project.

Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, and file extensions.

Constant width

Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.

Constant width bold

Shows commands or other text that should be typed literally by the user.

Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.

Using Code Examples

Supplemental material (code examples, exercises, etc.) is available for download at http://evolutionaryarchitecture.com.

If you have a technical question or a problem using the code examples, please send email to [email protected].

This book is here to help you get your job done. In general, if example code is offered with this book, you may use it in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.

We appreciate, but generally do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “Building Evolutionary Architectures, 2nd edition, by Neal Ford, Rebecca Parsons, Patrick Kua, and Pramod Sadalage (O’Reilly). Copyright 2023 Neal Ford, Rebecca Parsons, Patrick Kua, and Pramod Sadalage, 978-1-492-09754-9.”

If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at [email protected].

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Additional Information

The authors maintain a companion website for this book at http://evolutionaryarchitecture.com.

Acknowledgments

The authors would like to give vociferous thanks to our colleagues who provided the outlines and inspirations for the many fitness function case studies presented within. In no particular order, thanks to Carl Nygard, Alexandre Goedert, Santhoshkumar Palanisamy, Ravi Kumar Pasumarthy, Indhumathi V., Manoj B. Narayanan, Neeraj Singh, Sirisha K., Gireesh Chunchula, Madhu Dharwad, Venkat V., Abdul Jeelani, Senthil Kumar Murugesh, Matt Newman, Xiaojun Ren, Archana Khanal, Heiko Gerin, Slin Castro, Fernando Tamayo, Ana Rodrigo, Peter Gillard-Moss, Anika Weiss, Bijesh Vijayan, Nazneen Rupawalla, Kavita Mittal, Viswanath R., Dhivya Sadasivam, Rosi Teixeira, Gregorio Melo, Amanda Mattos, and many others whose names we failed to capture.

Neal would like to thank all the attendees of the various conferences at which he has spoken over the last few years to help hone and revise this material in person and especially online, due to the unusual circumstances of a global pandemic. Thanks to all the front-line workers who stepped up bravely to help us all through this difficult time. He would also like to thank the technical reviewers who went above and beyond to provide excellent feedback and advice. Neal would also like to thank his cats, Amadeus, Fauci, and Linda Ruth, for providing useful distractions that often led to insights. Cats never dwell on the past or future; they are always in the current moment, so he uses his time with them to join their presence in the here and now. Thanks also to our outdoor neighborhood “cocktail club,” which started as a community way to see friends and has evolved into the neighborhood brain trust. And finally, Neal would like to thank his long-suffering wife, who endures his travel, and then the abrupt absence of travel, and other professional indignities with a smile.

Rebecca would like to thank all the colleagues, conference attendees and speakers, and authors who have, over the years, contributed ideas, tools, and methods and asked clarifying questions about the field of evolutionary architecture. She echoes Neal’s thanks to the technical reviewers for their careful reading and commentary. Further, Rebecca would like to thank her coauthors for all the enlightening conversations and discussions while working together on this book. In particular, she thanks Neal for the great discussion, or perhaps debate, they had several years ago regarding the distinction between emergent and evolutionary architecture. These ideas have come a long way since that first conversation.

Patrick would like to thank all his colleagues and customers at ThoughtWorks, who have driven the need and provided the test bed to articulate the ideas in building evolutionary architecture. He also would like to echo Neal’s and Rebecca’s thanks to the technical reviewers, whose feedback helped to improve the book immensely. Finally, he would like to thank his coauthors for the past several years and for the opportunity to work closely together on this topic, despite the numerous time zones and flights that made meeting in person the rare occasion.

Pramod would like to thank all his colleagues and clients who have always provided the space and time to explore new ideas and to push new ideas and thinking. He would like to thank his coauthors for thoughtful discussions ensuring that all aspects of architecture are considered. He also would like to thank the reviewers—Cassandra Shum, Henry Matchen, Luca Mezzalira, Phil Messenger, Vladik Khononov, Venkat Subramanium, and Martin Fowler—for thoughtful comments that helped the authors immensely. And finally, he would like to thank his daughters, Arula and Arhana, for the joy they bring into his life, and his wife, Rupali, for all her love and support.