Most Terraform lessons teach variables as configuration knobs.
But variables are not knobs.
They are identity entry points into your dependency graph.
When you design a module, you are not just exposing inputs.
You are defining how meaning enters the system.
In this lesson, we examine:
- Why vague variable names create semantic instability
- How type constraints enforce structure before planning
- How defaults silently encode policy decisions
- Why
sensitivecontrols exposure, not encryption - How too many variables increase coupling and long-term risk
Terraform will faithfully construct whatever boundary you define.
The question is not whether the graph will work.
The question is whether the interface preserves clarity, responsibility, and stability.
Clean variable interfaces produce stable systems.