Heart of Clojure

September 18 & 19, Leuven, Belgium.

Staring into the PLFZABYSS - From the IBM AS/400 to Clojure & Datomic


Starting in 2021, we naively took on the task of bringing mission-critical legacy systems in the automotive logistics sector into the modern era.

This experience report covers our eventually successful live migration from the IBM AS/400 to Clojure and Datomic. We look at both the technical and human organizational challenges we faced and share our failures and learnings along the way.

Thousands of globally unique 8-character column names, green-screen terminal UIs, skunk work projects and personal drama — this talk has it all!

  • Context & background
    • The automotive logistics industry and its challenges
    • Initial state: High resistance from employees, mistrust, and outdated technology
  • Technical challenges
    • Dealing with very old systems (IBM AS400 & EDI)
    • Transitioning from terminal-based interfaces to modern UIs
    • Strategies for dealing with legacy data (using Clerk)
    • Data integrity & system reliability
  • The Human Factor
    • Organizational resistance and difficulty to convince clients of a gradual migration
    • Dishonesty & attempted sabotage
    • Agile vs. top-down (The Chaos Method™)
    • Strategies to build trust and foster collaboration (The Bavarian Method™)
  • The Journey
    • Incremental rollouts & parallel running
    • Skunkworks side-projects enable gradual migration
    • Benefits and pitfalls of using Clojure & Datomic
  • Day Zero
    • Lead-up week
    • What happens on switchover day?
    • Post-switchover support and optimization
  • Summary of key takeaways & Q/A


  • Philippa Markovics

    Philippa works as UI Designer and Frontend Lead at Nextjournal, mostly working on Clerk at the moment. Her main interests are in how we can make programming more tangible and data science more accessible. When she’s not working, you can find her planting food plots somewhere in the Austrian countryside.

  • Martin Kavalar

    Martin Kavalar is a co-founder at Nextjournal, a hybrid between startup and research lab trying to improve programming. Nextjournal makes a polyglot computational notebook with a focus on reproducibility and a variety of open source tools, including Clerk, a programmer’s assistant for Clojure.

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