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Aisalkyn Aidarova
Aisalkyn Aidarova

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PROJECT : Registry Module + Version Pinning

Goal

Use a Terraform Registry module, pin its version, and understand why.

What Certification Tests Here

  • Registry modules
  • source syntax
  • version constraint
  • Why pinning matters

Code (main.tf) 

provider "aws" {
  region = "us-west-1"
}

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"

  name = "cert-vpc"
  cidr = "10.0.0.0/16"

  azs             = ["us-west-1a"]
  public_subnets  = ["10.0.1.0/24"]
}
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Commands 

terraform init
terraform plan
terraform apply
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Exam Answers

Q: Why use version in module block?
✔️ Prevents breaking changes

Q: Where is module code stored locally?
✔️ .terraform/modules/

Q: What happens if version is removed?
✔️ Latest version may break infra

Interview Line

We pin registry module versions to avoid unexpected behavior caused by upstream changes.

PROJECT 4 — Remote State Consumption Between Teams

✅ Medium–large company standard

Goal

One team creates S3, another team reads it using remote state.

Team A — Infra Team (creates S3)

infra/main.tf 

terraform {
  backend "s3" {
    bucket = "tf-state-aj"
    key    = "infra/s3.tfstate"
    region = "us-west-1"
  }
}

provider "aws" {
  region = "us-west-1"
}

resource "aws_s3_bucket" "shared" {
  bucket = "shared-logs-aj"
}

output "bucket_name" {
  value = aws_s3_bucket.shared.bucket
}
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Team B — App Team (reads S3)

app/main.tf 

data "terraform_remote_state" "infra" {
  backend = "s3"

  config = {
    bucket = "tf-state-aj"
    key    = "infra/s3.tfstate"
    region = "us-west-1"
  }
}

output "bucket_from_infra" {
  value = data.terraform_remote_state.infra.outputs.bucket_name
}
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Exam Answers

Q: Does remote state create resources?
❌ No, it only reads

Q: Why remote state vs data source?
✔️ When resource is Terraform-managed elsewhere

Interview Line

We use terraform_remote_state to safely share outputs across team-owned Terraform projects.

PROJECT 5 — Module with Multiple Providers (Alias)

✅ Exam + real production

Goal

Create resources in two AWS regions using one module.

Root Module (main.tf) 

provider "aws" {
  alias  = "west"
  region = "us-west-1"
}

provider "aws" {
  alias  = "east"
  region = "us-east-1"
}

module "west_bucket" {
  source    = "./modules/s3"
  providers = { aws = aws.west }
  name      = "west-bucket-aj"
}

module "east_bucket" {
  source    = "./modules/s3"
  providers = { aws = aws.east }
  name      = "east-bucket-aj"
}
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Module (modules/s3/main.tf) 

variable "name" {}

resource "aws_s3_bucket" "this" {
  bucket = var.name
}
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Exam Answers

Q: When do we use provider alias?
✔️ Multi-region or multi-account

Q: Can child modules inherit providers?
✔️ Yes, unless overridden

Interview Line

Provider aliases allow us to deploy identical infrastructure across regions or accounts using the same module.

PROJECT 6 — Module Versioning + Upgrade Behavior

✅ Frequently misunderstood

Goal

Understand how module upgrades work.

Code 

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "~> 5.0"
}
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Upgrade Scenario 

terraform init -upgrade
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Exam Answers

Q: Does Terraform auto-upgrade modules?
❌ No

Q: What command upgrades modules?
✔️ terraform init -upgrade

Q: Where are versions locked?
✔️ .terraform.lock.hcl

Interview Line

Terraform locks module versions to ensure reproducible builds and requires explicit upgrade actions.

FINAL CERTIFICATION CHEAT SHEET (MEMORIZE)

Topic Status
Root vs Child modules ✅
Local modules ✅
Registry modules ✅
Module inputs/outputs ✅
Module reuse ✅
for_each + modules ✅
Remote state ✅
Provider alias ✅
Version pinning ✅
Upgrade behavior ✅

What You Are Ready For Now

You can now:

  • Answer any Terraform module question
  • Pass Terraform Associate module objectives
  • Explain real production usage
  • Teach this to students

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