Terraform Input Variables, Outputs, and Variable Precedence on AWS

Terraform configurations become reusable and maintainable when values are parameterized through input variables instead of hard-coded into resource blocks. Input variables support type constraints, default values, descriptions, and validation rules, giving teams a single interface for customizing deployments across environments. Equally important is understanding variable precedence -- Terraform evaluates values from environment variables, terraform.tfvars files, command-line flags, and variable definition files in a specific order, and the last value wins. Outputs complement this by exposing computed attributes from deployed resources so they can be consumed by other configurations or displayed after an apply.

In this lab, you will declare input variables with type constraints and defaults in a Terraform project targeting AWS, create a terraform.tfvars file to override defaults, demonstrate variable precedence by supplying values through multiple mechanisms, deploy a DynamoDB table parameterized by those variables, and define output values that expose the table name and ARN after a successful apply.

Objectives

Upon completion of this beginner level lab, you will be able to:

• Declare input variables with type constraints, defaults, and descriptions in a variables.tf file
• Override default variable values using terraform.tfvars and the -var command-line flag
• Explain and demonstrate the Terraform variable precedence order
• Deploy an AWS DynamoDB table parameterized by input variables
• Define and query output values that expose resource attributes after terraform apply

Who is this lab for?

This lab is designed for:

• Cloud engineers learning how to parameterize Terraform configurations for multiple environments
• DevOps practitioners who need to understand how variable precedence affects automated deployments
• Terraform Associate candidates preparing for exam objectives covering variables, outputs, and configuration