large-size-infrastructure-with-terraform.md

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.

{% hint style="info" %} In a large project like described here the benefits of using Terragrunt becomes very visible. See Code Structures examples with Terragrunt. {% endhint %}

{% hint style="success" %}

• 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) {% endhint %}

{% hint style="warning" %} 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. {% endhint %}