Imagine you’re expanding your Lego city. Sometimes you want to build a fixed number of identical houses (like 3 small cottages). Other times, you want to build a set of unique houses, each with its own name and design.

Terraform gives you two looping tools for this: count (repeat something a fixed number of times) and for_each (repeat something for each item in a list or map). Together, they make your infrastructure modular, scalable, and dynamic.

Key Concepts

1. Count Loops

• Definition: Creates multiple instances of a resource based on a number.
• Result: Creates 3 EC2 instances.
• Accessing: aws_instance.web[0], aws_instance.web[1], aws_instance.web[2].
• Use case: Fixed repetition (e.g., 3 identical servers).

resource "aws_instance" "web" {
  count         = 3
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
}

2. For‑Each Loops

• Definition: Creates multiple instances of a resource based on items in a list or map.
• Result: Creates 3 EC2 instances, each tagged with dev, staging, prod.
• Accessing: aws_instance.web["dev"], aws_instance.web["staging"], aws_instance.web["prod"].
• Use case: Unique resources with identifiers.

resource "aws_instance" "web" {
  for_each = toset(["dev", "staging", "prod"])
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  tags = {
    Name = each.key
  }
}

3. Comparison Table

Hands‑On Lab / Demo

Lab: Deploying Servers with Count vs For‑Each

variable "environments" {
  default = ["dev", "staging", "prod"]
}

resource "aws_instance" "foreach_example" {
  for_each = toset(var.environments)
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  tags = {
    Name = each.key
  }
}

→ Creates dev, staging, and prod servers.

resource "aws_instance" "count_example" {
  count         = 2
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"
  tags = {
    Name = "server-${count.index}"
  }
}

→ Creates server-0 and server-1.

Pro Tips & Best Practices

• Use count for simple repetition with no unique identifiers.
• Use for_each when resources need distinct names or attributes.
• Avoid mixing count and for_each in the same resource as it gets confusing.
• Always prefer readability - choose the loop that makes code clearer.
• Document loop usage in module README for maintainability.

Summary & Cheatsheet

• Count: Repeat resources by number → count.index.
• For‑Each: Repeat resources by list/map → each.key, each.value.
• Best practice: Use count for fixed repetition, for_each for unique identifiers.

Quick mnemonic: Count = Numbers, For‑Each = Names

The Hackers Notebook

Loops are Terraform’s scaling tools. count lets you repeat resources by number, while for_each lets you create resources for each item in a list or map. Together, they make your infrastructure flexible, scalable, and easier to manage.