# vpc — VPC with subnets and routing

> **Module kind:** L1 primitive  |  **Version:** 1.0.0

A VPC with one subnet per availability zone and a route table with a
default route through an internet gateway. The networking foundation
that other modules (ALB, ECS service) reference for subnet ids.

## Resources

| Resource | Type | Purpose |
|----------|------|---------|
| vpc | `aws_vpc` | The VPC itself |
| subnet | `aws_subnet` | One subnet per availability zone |
| route_table | `aws_route_table` | Route table with default route 0.0.0.0/0 |
| internet_gateway | `aws_internet_gateway` | IGW for public internet access |
| route_table_association | `aws_route_table_association` | Binds subnet to route table |

## Inputs

| Name | Type | Required | Default | Description |
|------|------|----------|---------|-------------|
| `cidr` | string | yes | — | VPC CIDR block, e.g. `10.0.0.0/16` |
| `azs` | string | yes | — | Comma-separated availability zones, e.g. `us-east-1a,us-east-1b` |
| `name` | string | yes | — | Name tag for the VPC and child resources |
| `region` | string | yes | — | AWS region the VPC is created in |

## Outputs

| Name | Type | Description |
|------|------|-------------|
| `vpc_id` | string | The VPC id |
| `subnet_ids` | string | Comma-separated subnet ids |

## Usage

```json
{
  "id": "vpc",
  "type": "aws:ec2:vpc",
  "module": "vpc@1.0.0",
  "inputs": {
    "cidr": "10.0.0.0/16",
    "azs": "us-east-1a,us-east-1b",
    "name": "acdl-microservice",
    "region": "us-east-1"
  }
}
```

The `azs` input is split on comma; one subnet is created per zone. The
route table gets a default route `0.0.0.0/0` → internet gateway. Other
modules reference `subnet_ids` for their network placement.

## Compliance extension points

- **VPC Flow Logs** — add `aws_flow_log` + CloudWatch Logs group / S3 destination (SOX ITGC, SOC2 CC7.2, HIPAA §164.312(b), DORA ICT risk logging).
- **Private subnets + NAT gateway** — add private subnets with a NAT gateway so ECS tasks don't need public IPs (SOC2 CC6.6, PCI-DSS 1.3, HIPAA network isolation).
- **VPC endpoints** — add S3, ECR, KMS, DynamoDB, CloudWatch interface/gateway endpoints to keep traffic off the public internet (SOC2 CC6.7, GDPR Art.32(1)(a), DORA ICT third-party risk).
- **Security groups** — add `aws_security_group` as a first-class sub-resource (currently missing; needed for all regulated deployments) (SOC2 CC6.6, PCI-DSS 1.2).
- **Network ACLs** — add `aws_network_acl` for subnet-level segmentation (PCI-DSS 1.3).

## Versioning

`1.0.0` — interface MAJOR, behavior MINOR, lifecycle PATCH. MAJOR bumps
require a new registry entry (immutable publication); old entries enter
a 12-month deprecation window.