Infrastructure as Code — Basics
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Core answer
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Interview answer
Infrastructure as Code means defining infrastructure resources and relationships in version-controlled source rather than relying only on manual console steps. A tool such as Terraform or CloudFormation plans and applies those definitions through cloud APIs.
For example, a module can define the network, security rules, container service, load balancer, and database settings for an order API. A pull request shows the proposed source change, and a plan shows whether the provider will create, update, or replace resources before an authorized apply.
The value is repeatability, review, traceability, and automation. It is not a guarantee of an similarly configured environment: provider versions, region capabilities, external state, existing data, and manual changes still matter. IaC also does not restore database contents by itself. I would pair it with locked versions, protected state, least-privilege credentials, reviewed plans, drift detection, backups, and tested recovery.
Infrastructure as Code — Basics
Direct Answer
Infrastructure as Code means defining cloud resources like servers, databases, and networks in configuration files instead of manually clicking through the AWS console. It's used in cloud deployments because it makes infrastructure reproducible, version-controlled in Git, and automated through CI/CD pipelines. Tools like Terraform and AWS CloudFormation turn infrastructure into code that can be reviewed, tested, and changed through reviewed, automated plans.
Code Example
// Define RDS database and ECS cluster for Spring Boot app
resource "aws_db_instance" "orders_db" {
identifier = "orders-database"
engine = "postgres"
engine_version = "15.3"
instance_class = "db.t3.micro"
allocated_storage = 20
username = "admin"
password = var.db_password // From environment variable
}
resource "aws_ecs_cluster" "app_cluster" {
name = "spring-boot-cluster"
}
resource "aws_ecs_task_definition" "app" {
family = "order-service"
requires_compatibilities = ["FARGATE"]
cpu = "256"
memory = "512"
container_definitions = jsonencode([{
name = "order-service"
image = "123456.dkr.ecr.us-east-1.amazonaws.com/order-service:latest"
environment = [
{name = "DB_HOST", value = aws_db_instance.orders_db.endpoint}
]
}])
}
Common Mistakes & Pitfalls
- Calling configuration and data identical: IaC defines resources; backups/migrations restore stateful data.
- Running apply automatically with broad credentials and no reviewed plan: use least privilege and approval for material changes.
- Losing or racing the state file: use protected remote state and locking where the tool supports it.
- Allowing invisible console drift: detect it and import, revert, or reconcile it deliberately.
Check your understanding
Answer these without looking back at the article.
- What is Terraform and how does it differ from Ansible?
- What is AWS CDK and how does it let Java developers write infrastructure?
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