Module Composition: Passing Data Between Modules 🔧 Terraform Core ⭐ Intermediate Module Outputs Cross-Module References depends_on with Modules Scenario You have two modules: one creates an S3 bucket, the other creates an SSM parameter that stores the bucket name. The…

Module Sources and Versioning 🔧 Terraform Core ⭐ Intermediate Module Sources Terraform Registry Git Source version constraint Scenario Your team has been using a local module for S3 buckets. Now you want to try a public module from the Terraform…

Writing Your First Terraform Module 🔧 Terraform Core ⭐ Intermediate module Module Structure source Module Inputs/Outputs Scenario You’ve been copying the same S3 bucket + versioning + encryption config across 6 different projects. Every copy has slight variations and bugs.…

precondition, postcondition and check Blocks 🔧 Terraform Core ⭐ Intermediate precondition postcondition check block assert Custom Validation Scenario You want to catch errors at three different levels: before a resource is created (bad assumptions), after it’s created (unexpected cloud behavior),…

null_resource and terraform_data: Actions Without Cloud Resources 🔧 Terraform Core ⭐ Intermediate null_resource terraform_data triggers triggers_replace Scenario After Terraform creates an S3 bucket, you need to run a registration script. But the script isn’t tied to any specific cloud resource…

Provisioners: local-exec, remote-exec and Why They Are a Last Resort 🔧 Terraform Core ⭐ Intermediate local-exec remote-exec file provisioner on_failure self destroy-time Scenario After creating an S3 bucket, you need to run a local script that registers the bucket in…

Lifecycle Rules: Controlling Resource Behavior 🔧 Terraform Core ⭐ Intermediate lifecycle create_before_destroy prevent_destroy ignore_changes replace_triggered_by Scenario Your production S3 bucket must never be accidentally deleted by terraform destroy. When renaming a bucket, you want the new one created before the…

templatefile() and file(): External Content in Terraform 🔧 Terraform Core ⭐ Intermediate templatefile() file() Heredoc Syntax User Data Scenario You need to pass a startup script to an EC2 instance. The script is complex — it installs packages, configures services,…

Collection Functions: Maps, Lists and Transformations 🔧 Terraform Core ⭐ Intermediate merge() flatten() lookup() keys() / values() coalesce() contains() Scenario You’re managing tags across multiple resources, flattening nested lists of subnets, looking up values from configuration maps, and handling defaults…