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Terraform Best Practices: IaC at Scale (2025)

Oct 26, 2025•
terraformiaccloudsecurity
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Terraform remains the de facto standard for IaC. This guide covers patterns that reduce drift, improve reuse, and keep teams safe.

Executive summary

  • Compose with versioned modules; pin providers
  • Separate state per env; remote state with locking
  • Validate/plan in CI; policy as code; drift alerts

Modules

module "vpc" {
  source  = "git::ssh://git/repo//modules/vpc?ref=v1.2.3"
  cidr    = var.vpc_cidr
  subnets = var.subnets
}
  • Semantic tags; minimal inputs/outputs; docs and examples

State

  • Use remote backends (S3+Dynamo, GCS, Azurerm) with locking; least-privilege

Workspaces and environments

  • Option A: directory per env; Option B: workspaces; avoid mixing

CI/CD

steps:
  - run: terraform fmt -check
  - run: terraform validate
  - run: terraform plan -out tf.plan
  - run: conftest test policy/

Policy as code

  • Sentinel/Open Policy Agent; deny public S3, enforce tags, restrict instance classes

Secrets

  • Never in tfvars; use vault/SM/KeyVault; inject at apply time

Drift detection

  • Nightly plan; alert on changes; task to reconcile or accept

FAQ

Q: Workspaces or directories?
A: Directories for clarity and separate pipelines; workspaces ok for small teams but harder to isolate.

  • Kubernetes Cost Optimization: /blog/kubernetes-cost-optimization-finops-strategies-2025
  • GitOps Strategies: /blog/gitops-argocd-flux-kubernetes-deployment-strategies
  • Multi-Cloud Strategy: /blog/multi-cloud-strategy-vendor-lock-in-prevention-2025
  • AWS Architecture Patterns: /blog/aws-architecture-patterns-well-architected-framework
  • Cloud Migration: /blog/cloud-migration-strategies-lift-shift-refactor-2025

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