Beyond Terraform Modules: Infrastructure Design by Contract

The Hidden Tax of Module Stitching Four Pillars of Infrastructure Design by Contract 1. Contract-Led Composition: Explicit Interfaces Between Components 2. Environment-Aware by Design: Contracts Across Environments 3. Progressive Rollouts for Infrastructure: Versioned Contracts 4. Developer Experience That Preserves Governance: Preconditions and Postconditions From Configuration to Contract-Driven Infrastructure Posted on September 2, 2025 by Anshul Sao, Co-Founder & CTO at Facets. cloud CNCF projects highlighted in this post It’s 2AM. You’re staring at a failed deployment pipeline, trying to figure out why your EKS cluster can’t find the right subnets. You’ve checked the variables, verified the outputs, and triple-checked your depends_on statements. Everything looks correct, yet it still fails. This scenario plays out daily across organizations that have adopted Terraform. While modules promised composable, reusable infrastructure, the reality has become a complex web of string-matching, implicit dependencies, and tribal knowledge. How much of your team’s time is spent debugging module connections rather than delivering value? Every time a team provisions infrastructure for a new service or application, they pay an invisible tax in cognitive overhead: For each input a module needs, someone must make critical decisions: Is this value a hard-coded constant? A data lookup? An output from another module? The answer differs for every project and environment, so this decision tree must be rebuilt from scratch each time.