Multi-Region AWS Infrastructure

terraform# provider.tf
provider "aws" {
  region = var.primary_region
  alias  = "primary"
}

provider "aws" {
  region = var.secondary_region
  alias  = "secondary"
}

terraform# VPCs
module "vpc_primary" {
  source  = "terraform-aws-modules/vpc/aws"
  providers = { aws = aws.primary }
  name    = "primary-vpc"
  cidr    = "10.0.0.0/16"
  azs     = ["us-east-1a", "us-east-1b"]
  public_subnets  = ["10.0.1.0/24", "10.0.2.0/24"]
  private_subnets = ["10.0.3.0/24", "10.0.4.0/24"]
}

module "vpc_secondary" {
  source  = "terraform-aws-modules/vpc/aws"
  providers = { aws = aws.secondary }
  name    = "secondary-vpc"
  cidr    = "10.1.0.0/16"
  azs     = ["us-west-2a", "us-west-2b"]
  public_subnets  = ["10.1.1.0/24", "10.1.2.0/24"]
  private_subnets = ["10.1.3.0/24", "10.1.4.0/24"]
}

terraform# Launch Template + Auto Scaling
resource "aws_launch_template" "app" {
  name_prefix   = "app-template"
  image_id      = var.ami_id
  instance_type = "t3.micro"
}

resource "aws_autoscaling_group" "asg_primary" {
  provider = aws.primary
  desired_capacity     = 2
  max_size             = 4
  min_size             = 2
  vpc_zone_identifier  = module.vpc_primary.private_subnets
  launch_template {
    id      = aws_launch_template.app.id
    version = "$Latest"
  }
  tag {
    key                 = "Name"
    value               = "primary-asg"
    propagate_at_launch = true
  }
}

terraform# Load Balancer
resource "aws_lb" "alb_primary" {
  provider = aws.primary
  name     = "primary-alb"
  internal = false
  load_balancer_type = "application"
  subnets = module.vpc_primary.public_subnets
}

resource "aws_lb_target_group" "tg_primary" {
  provider = aws.primary
  name     = "primary-tg"
  port     = 80
  protocol = "HTTP"
  vpc_id   = module.vpc_primary.vpc_id
}

resource "aws_lb_listener" "listener_primary" {
  provider = aws.primary
  load_balancer_arn = aws_lb.alb_primary.arn
  port              = 80
  protocol          = "HTTP"
  default_action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.tg_primary.arn
  }
}

terraform# Route 53 Failover
resource "aws_route53_record" "primary" {
  zone_id = var.zone_id
  name    = "app.example.com"
  type    = "A"
  set_identifier = "primary"
  failover_routing_policy {
    type = "PRIMARY"
  }
  alias {
    name                   = aws_lb.alb_primary.dns_name
    zone_id                = aws_lb.alb_primary.zone_id
    evaluate_target_health = true
  }
}

resource "aws_route53_record" "secondary" {
  zone_id = var.zone_id
  name    = "app.example.com"
  type    = "A"
  set_identifier = "secondary"
  failover_routing_policy {
    type = "SECONDARY"
  }
  alias {
    name                   = aws_lb.alb_secondary.dns_name
    zone_id                = aws_lb.alb_secondary.zone_id
    evaluate_target_health = true
  }
}

terraform# Disaster Recovery (S3 + RDS)
resource "aws_s3_bucket" "primary" {
  provider = aws.primary
  bucket   = "primary-app-bucket"
}

resource "aws_s3_bucket_replication_configuration" "replication" {
  provider = aws.primary
  bucket   = aws_s3_bucket.primary.id
  role     = aws_iam_role.replication.arn

  rules {
    id     = "replication"
    status = "Enabled"
    destination {
      bucket        = aws_s3_bucket.secondary.arn
      storage_class = "STANDARD"
    }
  }
}

resource "aws_db_instance" "primary_rds" {
  provider = aws.primary
  engine   = "mysql"
  instance_class = "db.t3.micro"
  allocated_storage = 20
  name     = "appdb"
  username = "admin"
  password = var.db_password
}

resource "aws_db_instance" "secondary_rds" {
  provider = aws.secondary
  replicate_source_db = aws_db_instance.primary_rds.arn
}

terraform# Commands
terraform init
terraform validate
terraform plan -var="primary_region=us-east-1" -var="secondary_region=us-west-2" -var="ami_id=ami-0abcd1234efgh5678" -var="zone_id=Z123456789" -var="db_password=SuperSecret123"
terraform apply -auto-approve