DevNexus 2019 – Why and How of Evolutionary Design – Rebecca Parsons

See the table of contents for my other blog posts from the conference

  • How plan long tern architecture when under constant change
  • if on unicycle, focus on not falling. We are on the unicycle
  • evolutionary architecture is guided change
  • have to agree on what consistutes good. Not all systems need same level of security reliability, etc

Fitness function

  • how we define good.
  • Needs to be clear so no disagreement on whether the system meets. So cant just say “maintainability”
  • examples: manual vs automated, temporal, triggered vs continuous, static vs dynamic
  • think of us a test
  • chaos monkey is like a test. You know configured correctly


  • Make decisions at last responsible moment. Know the nost then
  • evolvability needs to be a first class citizen
  • how communicate across non functional requirements
  • minimize logic to minimize change. Dont do unnecessary work
  • testability
  • Conway’s law. The communication structure of your system will mimic that of organization. Communication silos in an org result in broken ntegration


  • Continuous Delivery
  • Database refactoring – can’t migrate a system if you are being held hostage by the data
  • orchestration – the orchestra follows the conductor.
  • Consumer driven contracts. – dont have to think about until test breaks

Kinds of monoloiths

  • Ball of mud
  • layered monolyth. Can’t change without coordinating across all layers. reduce costs by standarizing everything. Slows things down. IT is an enabler and not just a cost center
  • modular monolyth
  • micro kernel architecture is only adaptable in ways you predicated. Also have to write the adapters so have more code/bugs

My take

Good talk. It was interesting and applies to almost everyone. I particularly liked the principles. I would have liked to see the slides after it got stuck. The talk was clear. But it is a long day and would have been easier to follow by visually seeing the points on principles and techniques. Im glad she acknowledged the slides not working at leaat

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