> "Modernising the payroll integration is blocked because we would have to reverse-engineer it first — the people who built it left a decade ago." ^pain A collective survivability pain specific to old systems. Critical programs, bespoke scripts, operator tricks live in a few engineers' heads. Modernisation budgets balloon because just understanding current behaviour requires reverse-engineering. Distinct from generic tribal knowledge — this is specifically tribal knowledge *about a system whose original author is unreachable*. ## Discovery questions - "How much of your production system's current behaviour is documented versus 'just the way it works'?" - "If you were forced to rewrite a legacy subsystem tomorrow, how much of the existing behaviour could you reconstruct from documentation alone?" ^discovery-questions ## Examples - During the COVID-19 unemployment surge, New Jersey's governor publicly appealed for COBOL programmers - the state's 40-year-old unemployment system ran on legacy mainframes few people understood.[^1] - The IRS still relies on 1960s-era COBOL systems like the Individual Master File; modernisation repeatedly delayed partly because of the difficulty of understanding old code.[^2] - Commonwealth Bank of Australia spent ~5 years and hundreds of millions migrating off a core COBOL banking platform - hard to replace legacy systems whose behaviour was poorly documented.[^3] - U.S. Navy ERP modernisation sank ~$1B into failed pilots replacing 280 legacy mainframe/minicomputer applications, partly because behaviour and integrations were inadequately understood.[^4] - Pentagon and DISA highlight that many DoD systems run on legacy code whose original authors are "long gone", prompting AI-assisted modernisation projects to reconstruct them.[^5] [^1]: https://statescoop.com/coronavirus-new-jersey-needs-cobol-coders-unemployment [^2]: https://taxpolicycenter.org/briefing-book/what-technology-does-irs-use [^3]: https://codemanship.wordpress.com/2020/04/21/why-cobol-may-be-the-language-in-your-future [^4]: https://www.computerwoche.de/article/2620123/us-gov-t-navy-sank-1b-into-four-failed-erp-pilots.html [^5]: https://defensescoop.com/2024/09/12/pentagon-artificial-intelligence-modernize-legacy-code-john-hale