Large-size infrastructure with Terraform

Source: https://github.com/antonbabenko/terraform-best-practices/tree/master/examples/large-terraform

This example contains code as an example of structuring Terraform configurations for a large-size infrastructure which uses:

  • 2 AWS accounts

  • 2 regions

  • 2 separate environments (prod and stage which share nothing). Each environment lives in separate AWS account and span resources between 2 regions

  • Each environment uses different version of off-the-shelf infrastructure module (alb) sourced from Terraform Registry

  • Each environment uses the same version of internal module modules/network since it is sourced from a local directory.

In a large project like described here the benefits of using Terragrunt becomes very visible. See Code Structures examples with Terragrunt.

  • Perfect for projects where infrastructure is logically separated (separate AWS accounts)

  • Good when there is no is need to modify resources shared between AWS accounts (one environment = one AWS account = one state file)

  • Good when there is no need in orchestration of changes between environment

  • Good when infrastructure resources are different per environment on purpose and can't be generalised (eg, some resources are absent on one environment or in some regions)

As project grows, it will be harder to keep these environments up-to-date between each other. Consider using of infrastructure modules (off-the-shelf or internal) for repeatable tasks.