Principles and Techniques of Evolutionary Architecture Rebecca Parsons Chief Technology Officer ThoughtWorks

Principles of evolutionary architecture Why should I care? Emergent design vs evolutionary architecture How to achieve an evolutionary architecture in practice Techniques of evolutionary architecture Agenda

It’s harder to predict the future Expectations for pace of change are increasing rapidly Business model lifetimes are shortening If you miss your minute of fame... Why Should I Care?

Evolutionary Architecture and Emergent Design Evolutionary versus Emergent Design and Architecture

Postel’s Law Last responsible moment Architect and develop for evolvability Conway’s Law Architect for testability Principles of Evolutionary Architecture

Minimizes technical debt from complexity Delay decisions as long as you can, but no longer Maximizes the information you have Evolutionary, neither emergent nor based on guesswork Decide early what your drivers are, and prioritize decisions accordingly Last Responsible Moment

Consider data lifecycle and ownership Sensible breakdown of functionality Lightweight tooling and documentation Appropriate coupling Architect for Evolvability

Software internal quality metrics focusing on ease of change Find hotspots and focus efforts there Measure continually, focusing on trends Develop for Evolvability

Reversability

Only validate what you need Be conservative in what you send Be liberal in what you receive Use version changes when a contract must be broken Holds for any information exchange Postel’s Law

Business sensible components Aiming towards testability produces a well- architected system Messaging infrastructure used for messaging, not business logic Build pipelines support the volume Testing at many levels, including contract Architect for Testability

Broken communications imply complex integration Organizations design systems reflecting their communication structures If you don’t want your product to look like your organization, change your organization (or your product) Silos often result in broken communication Conway’s Law

Database Refactoring Continuous Delivery Choreography Contract Testing Techniques

Changes compose in the same way functions compose De-compose big change into series of small changes Each change is a refactoring/migration pair (or triple if you include access code) And apply in the various environments during promotion And of course, version control the changes Database Refactoring

Automate testing at all levels Automate environments &configurations Automate builds and deployments and use continuous integration Just because you CAN release at any time doesn’t mean you HAVE to Deployment should be boring!! Continuous Delivery

Maximizes parallel independent work Acceptance tests at the systems’ interface Documents assumptions made One traditional role of Enterprise Architect Used in conjunction with Postel’s Law Contract Testing

Individuals perform to the vision without a conductor As opposed to orchestration Scripted outcomes and vision Introduces new kinds of failure scenarios Distributes authority about interactions Choreography

Understand various forms of technical debt Define your architectural fitness function Delay your decisions as long as you can Create and maintain the testing safety net Implement evidence based re-use Evolutionary Architecture

Thank you!