Terraform Modules

The multi-region shopping mall platform consists of 17 reusable Terraform modules. Each module is responsible for a specific infrastructure domain and is used identically across both regions.

Module Structure

Complete Module List

#	Module Name	Path	Resource Count	Description
1	vpc	networking/vpc	~15	VPC, Subnets, NAT Gateway, Internet Gateway
2	transit-gateway	networking/transit-gateway	~5	Transit Gateway, VPC Attachments
3	security-groups	networking/security-groups	~12	Service-specific Security Groups
4	kms	security/kms	~8	Service-specific KMS Keys (Aurora, DocDB, MSK, etc.)
5	secrets-manager	security/secrets-manager	~10	Database Credentials
6	iam	security/iam	~20	Service Roles and Policies
7	eks	compute/eks	~35	EKS Cluster, Add-ons, IRSA
8	alb	compute/alb	~10	Application Load Balancer
9	aurora-global	data/aurora-global	~12	Aurora PostgreSQL Global Database
10	documentdb-global	data/documentdb-global	~10	DocumentDB Global Cluster
11	elasticache-global	data/elasticache-global	~8	ElastiCache Valkey Global Datastore
12	msk	data/msk	~15	MSK Kafka Cluster, Replicator
13	opensearch	data/opensearch	~12	OpenSearch Domain
14	s3	data/s3	~10	S3 Buckets, Replication Rules
15	cloudfront	edge/cloudfront	~5	CloudFront Distribution
16	waf	edge/waf	~8	WAF v2 Web ACL
17	route53	edge/route53	~10	DNS Records, Health Checks
18	cloudwatch	observability/cloudwatch	~25	Dashboards, Alarms, Log Groups
19	xray	observability/xray	~5	X-Ray Groups, Sampling Rules
20	tempo-storage	observability/tempo-storage	~8	Tempo S3 Bucket, IAM Role

Module Details

1. VPC Module

Configures the network foundation infrastructure.

module "vpc" {
  source = "../../../modules/networking/vpc"

  environment          = var.environment
  region               = var.region
  vpc_cidr             = "10.0.0.0/16"
  availability_zones   = ["us-east-1a", "us-east-1b", "us-east-1c"]
  public_subnet_cidrs  = ["10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24"]
  private_subnet_cidrs = ["10.0.11.0/24", "10.0.12.0/24", "10.0.13.0/24"]
  data_subnet_cidrs    = ["10.0.21.0/24", "10.0.22.0/24", "10.0.23.0/24"]
}

Outputs:

• vpc_id - VPC ID
• public_subnet_ids - List of public subnet IDs
• private_subnet_ids - List of private subnet IDs
• data_subnet_ids - List of data subnet IDs

2. EKS Module

Provisions the Kubernetes cluster and related resources.

module "eks" {
  source = "../../../modules/compute/eks"

  cluster_name       = "multi-region-mall"
  cluster_version    = "1.29"
  region             = var.region
  vpc_id             = module.vpc.vpc_id
  private_subnet_ids = module.vpc.private_subnet_ids
}

Key Features:

• EKS Cluster (Kubernetes 1.29)
• OIDC Provider (for IRSA)
• Managed Add-ons: vpc-cni, coredns, kube-proxy, aws-ebs-csi-driver, aws-efs-csi-driver
• Service-specific IRSA Roles (20 microservices)

3. Aurora Global Module

Configures Aurora PostgreSQL-compatible Global Database.

module "aurora" {
  source = "../../../modules/data/aurora-global"

  environment           = var.environment
  region                = var.region
  is_primary            = true  # false in us-west-2
  global_cluster_identifier = "production-aurora-global"

  writer_instance_class = "db.r6g.2xlarge"
  reader_instance_class = "db.r6g.xlarge"
  reader_count          = 2
}

4. DocumentDB Global Module

Configures MongoDB-compatible DocumentDB Global Cluster.

module "documentdb" {
  source = "../../../modules/data/documentdb-global"

  environment              = var.environment
  region                   = var.region
  is_primary               = true
  global_cluster_identifier = "production-docdb-global"

  instance_class = "db.r6g.xlarge"
  instance_count = 3
}

5. ElastiCache Global Module

Configures Valkey 7.2-based Global Datastore.

module "elasticache" {
  source = "../../../modules/data/elasticache-global"

  environment      = var.environment
  region           = var.region
  is_primary       = true

  node_type                = "cache.r7g.xlarge"
  num_node_groups          = 3
  replicas_per_node_group  = 2
}

6. MSK Module

Configures Apache Kafka cluster and MSK Replicator.

module "msk" {
  source = "../../../modules/data/msk"

  environment           = var.environment
  region                = var.region
  kafka_version         = "3.5.1"
  broker_instance_type  = "kafka.m5.2xlarge"
  number_of_broker_nodes = 6
  ebs_volume_size       = 1000
}

7. OpenSearch Module

Configures OpenSearch domain for Korean language search.

module "opensearch" {
  source = "../../../modules/data/opensearch"

  environment          = var.environment
  region               = var.region

  master_instance_type  = "r6g.large.search"
  master_instance_count = 3
  data_instance_type    = "r6g.xlarge.search"
  data_instance_count   = 6
  ebs_volume_size       = 500
  enable_ultrawarm      = true
}

Module Dependencies

Module Development Guidelines

Standard File Structure

Each module follows this file structure:

modules/<category>/<module-name>/
├── main.tf          # Main resource definitions
├── variables.tf     # Input variables
├── outputs.tf       # Output values
└── versions.tf      # Provider version constraints (optional)

Variable Naming Conventions

# Environment variables (required)
variable "environment" {
  type        = string
  description = "Deployment environment (e.g., production, staging)"
}

variable "region" {
  type        = string
  description = "AWS region"
}

# Resource-specific variables
variable "instance_class" {
  type        = string
  description = "Instance class"
  default     = "db.r6g.large"
}

Tag Standards

tags = merge(var.tags, {
  Name        = "${var.environment}-<resource-name>"
  Environment = var.environment
  Module      = "<module-name>"
})

Next Steps

• EKS Cluster - EKS detailed configuration
• Aurora Global Database - Aurora global database
• Deployment Pipeline - Terraform CI/CD