Engineering Journal · 2026-08
The cost of hidden dependencies
Dependencies that live only in people's heads become change risk. Making them visible is cheaper than discovering them in an incident.
Where they hide
Cron on one host that 'everyone knows about'. A status column another service polls. A shared database table used as a queue. A spreadsheet that gates a nightly job. None of these appear in the architecture diagram until something breaks.
Why they get expensive
Change becomes slow because every edit needs tribal knowledge. Failures look random. New engineers inherit fear instead of a model. The system works — until the person who remembers the dependency is unavailable.
What to do instead
Prefer explicit edges: declared pipeline dependencies, versioned definitions, and an execution plane that records who triggered what. Hidden coupling will still appear; the discipline is to surface it when found, not to pretend the diagram was complete on day one.