Question 1

What is Infrastructure as Code and why is it useful?

Accepted Answer

Infrastructure as Code means creating and changing servers, networks and other cloud resources from code files instead of clicking in a console. The code lives in Git, so changes are reviewed, versioned and repeatable. You can rebuild an environment exactly, create identical dev, staging and prod setups, and see what will change before applying it. Terraform, CloudFormation and Pulumi are common tools.

Question 2

Explain the Terraform workflow.

Accepted Answer

terraform init downloads the providers and sets up the backend. terraform plan compares the code with the real infrastructure and the state file and shows what will be added, changed or destroyed. terraform apply makes those changes and updates the state, and terraform destroy removes everything the configuration manages. In a team, plan runs on the pull request and apply runs after approval.

Question 3

What is the Terraform state file?

Accepted Answer

The state file maps the resources in my code to the real resources in the cloud, with their IDs and attributes. Terraform uses it to know what already exists and what needs to change. It can contain sensitive values, so it should not be in Git. In a team it lives in a remote backend like S3 with encryption, versioning and locking, so two people cannot apply at the same time.

Question 4

What happens if two people run terraform apply at the same time?

Accepted Answer

Without locking they could both change the same resources and corrupt the state file, leaving it out of sync with the real infrastructure. That is why we use state locking. With an S3 backend, Terraform takes a lock (newer versions can lock in S3 itself, older setups use a DynamoDB table), and the second apply waits or fails with a lock error. Even better, only the CI pipeline runs apply.

Question 5

What are Terraform modules and why use them?

Accepted Answer

A module is a reusable group of Terraform resources with input variables and outputs, like a function. For example, one VPC module can create the network the same way for dev, staging and prod with different CIDRs. Modules reduce copy-paste, make standards easy to follow and are easier to test. I version them, for example with Git tags, so changing a module does not surprise every environment at once.

Terraform interview questions