Project — Web App Infrastructure

Let's think about this for a second

In a real-world project, you'll typically organize things by splitting the network layer (VPC, subnet), compute layer (server), and storage layer (database/bucket) into a module structure (`modules/network`, `modules/compute`, `modules/storage`) — each layer's output gets wired into the next layer's input, like passing the network module's subnet_id output into the compute module's subnet_id input. When you call the three modules in order inside the root config, Terraform figures out the dependency graph on its own.

Let's connect this to a real scenario

Split things into three modules: `modules/network/` (VPC + subnet), `modules/compute/` (server, taking subnet_id as an input), and `modules/storage/` (database) — then wire them together in the root `main.tf` with `module "network" { ... }` → `module "compute" { subnet_id = module.network.subnet_id }` → `module "storage" { ... }`. Run `terraform plan` and you can preview the resources for every layer all at once.

Each layer (network/compute/storage) gets its own dedicated module folder
Module outputs are wired into the next module's inputs
The root config calls all three modules and lets Terraform handle the dependency graph itself

Let's look at an example

hcl

# root main.tf
module "network" {
  source = "./modules/network"
}

module "compute" {
  source    = "./modules/compute"
  subnet_id = module.network.subnet_id
}

module "storage" {
  source = "./modules/storage"
}

output "web_server_ip" {
  value = module.compute.public_ip
}

You should see

$ terraform apply
module.network.aws_vpc.main: Creating...
module.network.aws_subnet.app: Creating...
module.compute.aws_instance.web: Creating...
module.storage.aws_db_instance.main: Creating...

Apply complete! Resources: 4 added, 0 changed, 0 destroyed.

Try it in 5 minutes

Create the three module folders (network/compute/storage) yourself and wire them together from the root config — then run `terraform plan` and verify all the layers are connected correctly.

A quick word of caution

Before you actually apply against a provider with real credentials/costs (like AWS) in a production project, read through `terraform plan` carefully — going over the free tier limit can rack up real charges.