Conditional expressions (ternary) in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Terraform Conditional Expression Output

What will be the value of instance_type after applying this Terraform configuration snippet?

Terraform

variable "environment" {
  default = "production"
}

locals {
  instance_type = var.environment == "production" ? "t3.large" : "t3.micro"
}

A "t3.large"

B "t3.micro"

C "production"

D null

💡 Hint

Check the condition comparing the environment variable.

The condition checks if environment equals "production". Since it does, the instance_type is set to "t3.large".

❓ Configuration

intermediate

Terraform Conditional Expression in Resource Count

Given the following Terraform resource snippet, how many instances of aws_instance will be created if var.deploy is false?

Terraform

variable "deploy" {
  default = false
}

resource "aws_instance" "example" {
  count = var.deploy ? 3 : 0
  ami           = "ami-123456"
  instance_type = "t2.micro"
}

A 0

B 1

C 3

D Error: count must be a positive integer

💡 Hint

Look at the count expression and the value of var.deploy.

Since var.deploy is false, the count expression evaluates to 0, so no instances are created.

❓ Architecture

advanced

Choosing Subnet Based on Environment Using Conditional Expression

In a Terraform module, you want to select a subnet ID based on the environment variable var.env. Which option correctly assigns subnet_id to "subnet-prod123" if var.env is "prod", and to "subnet-dev123" otherwise?

A subnet_id = var.env ? "subnet-prod123" : "subnet-dev123"

B subnet_id = var.env == "prod" ? "subnet-dev123" : "subnet-prod123"

C subnet_id = var.env == "prod" ? "subnet-prod123" : "subnet-dev123"

D subnet_id = var.env = "prod" ? "subnet-prod123" : "subnet-dev123"

💡 Hint

Check the equality operator and the order of values in the ternary expression.

Option C correctly uses the equality operator == and assigns the prod subnet when var.env is "prod".

❓ security

advanced

Conditional Expression for Enabling Encryption

You want to enable encryption on an AWS S3 bucket only if the variable var.enable_encryption is true. Which Terraform snippet correctly sets the server_side_encryption_configuration block conditionally?

A server_side_encryption_configuration = var.enable_encryption ? [] : [{ rule: { apply_server_side_encryption_by_default: { sse_algorithm: "AES256" } } }]

B server_side_encryption_configuration = var.enable_encryption ? [{ rule: { apply_server_side_encryption_by_default: { sse_algorithm: "AES256" } } }] : []

C server_side_encryption_configuration = var.enable_encryption == true ? [] : null

D server_side_encryption_configuration = var.enable_encryption ? null : [{ rule: { apply_server_side_encryption_by_default: { sse_algorithm: "AES256" } } }]

💡 Hint

Encryption block should be present only when enabled.

Option B correctly assigns the encryption configuration when var.enable_encryption is true, otherwise an empty list disables it.

✅ Best Practice

expert

Complex Conditional Expression for Instance Count

Consider this Terraform variable and resource snippet. What is the value of count for aws_instance.example if var.env is "staging" and var.scale_up is true?

Terraform

variable "env" {
  default = "staging"
}

variable "scale_up" {
  default = true
}

resource "aws_instance" "example" {
  count = var.env == "production" ? 5 : (var.scale_up ? 3 : 1)
  ami           = "ami-abc123"
  instance_type = "t3.medium"
}

A 0

B 5

C 1

D 3

💡 Hint

Evaluate the nested conditional expression step by step.

Since var.env is not "production", the count depends on var.scale_up. Because var.scale_up is true, count is 3.