Arguments and expressions in Terraform - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Configuration

intermediate

Terraform Expression Output Result

What is the value of the count local value after this Terraform expression is evaluated?

Terraform

variable "environment" {
  default = "prod"
}

variable "instance_count" {
  default = 3
}

locals {
  count = var.environment == "prod" ? var.instance_count * 2 : var.instance_count
}

A 0

B 3

C 6

D null

💡 Hint

Check the condition in the ternary expression and how it affects the count.

Since the environment is 'prod', the condition is true, so the count is instance_count * 2 = 3 * 2 = 6.

❓ service_behavior

intermediate

Terraform Conditional Argument Behavior

Given this Terraform resource snippet, what will be the value of the enable_monitoring argument when var.enable is false?

Terraform

resource "aws_instance" "example" {
  ami           = "ami-123456"
  instance_type = "t2.micro"

  enable_monitoring = var.enable ? true : false
}

A true

B false

C null

D Syntax error

💡 Hint

Look at the ternary expression and the value of var.enable.

Since var.enable is false, the ternary expression evaluates to false, so enable_monitoring is set to false.

❓ Architecture

advanced

Terraform Expression for Dynamic Subnet Selection

Which option correctly uses a Terraform expression to select all subnet IDs from var.subnets where the availability_zone equals var.az?

Terraform

variable "subnets" {
  type = list(object({
    id                = string
    availability_zone = string
  }))
}

variable "az" {
  type = string
}

locals {
  selected_subnets = <EXPRESSION>
}

A [for s in var.subnets : s.id if s.availability_zone == var.az]

B [for s in var.subnets : if s.availability_zone == var.az s.id]

C [for s in var.subnets : s.id where s.availability_zone == var.az]

D [for s in var.subnets : s.id if s.availability_zone = var.az]

💡 Hint

Terraform uses 'for' expressions with 'if' filters after the colon.

Option A correctly uses the syntax: [for item in list : expression if condition]. Other options have syntax errors.

❓ security

advanced

Terraform Sensitive Variable Expression

What will happen if you try to output a sensitive variable directly in Terraform like this?

Terraform

variable "db_password" {
  type      = string
  sensitive = true
}

output "password" {
  value = var.db_password
}

A Terraform will fail to plan due to sensitive output.

B Terraform will show the password value in the output.

C Terraform will throw a syntax error.

D Terraform will hide the password value and show <sensitive> in the output.

💡 Hint

Sensitive variables are handled specially in outputs.

Terraform masks sensitive output values by showing instead of the actual value.

✅ Best Practice

expert

Terraform Expression for Optional Argument with Default

Which option correctly sets an optional argument tags in a resource to use var.tags if defined, or an empty map if not defined?

Terraform

variable "tags" {
  type    = map(string)
  default = null
}

resource "aws_instance" "example" {
  ami           = "ami-123456"
  instance_type = "t2.micro"

  tags = <EXPRESSION>
}

A var.tags ?? {}

B var.tags ? var.tags : {}

C var.tags || {}

D var.tags != null ? var.tags : {}

💡 Hint

Terraform uses the null-coalescing operator for default values.

Option A uses the null-coalescing operator '??' which returns var.tags if not null, else {}.