ShortURLTerraformV2

An end‑to‑end, infrastructure‑as‑code template that deploys a serverless URL shortener on AWS using Terraform. It marries a low‑latency static front‑end with a scalable Lambda + DynamoDB back‑end, wrapped in CloudFront for global reach and SSL by default.

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🗺️ High‑Level Architecture

flowchart TD
    %% Edge Layer
    subgraph "AWS Edge (Global)"
        CF["CloudFront Distribution"]
    end

    %% Static Hosting
    subgraph "Static Site"
        S3["S3 Bucket
(OAI access)"]
    end

    %% Backend
    subgraph "API & Storage"
        LF["Lambda Function (Python)"]
        DB["DynamoDB Table"]
    end

    %% Monitoring
    subgraph "Observability"
        CW["CloudWatch Alarms"]
        SNS["SNS Topic"]
    end

    %% Flows
    User((Client Browser)) -->|HTTPS| CF
    CF -->|Assets| S3
    CF -->|Short URL| LF
    LF -->|Read/Write| DB
    LF --> CW
    CW --> SNS

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Key flows

• Static content (index.html, PNG logo) is served from the S3 bucket via CloudFront for low‑latency global delivery.
• Short URL hits reach the same CloudFront distribution; path‑based routing forwards them to the Lambda Function URL, which looks up the destination in DynamoDB and responds with an HTTP 301.
• Observability is handled with CloudWatch metrics and alarms (e.g., Lambda errors, 5XX rates) that can fan out alerts to an optional SNS topic.

GitHub renders Mermaid diagrams automatically. They respect the viewer’s dark/light theme.

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Repository Layout (TL;DR)

.
├── main.tf              # root orchestrator
├── variables.tf         # global knobs (region, tags, etc.)
├── outputs.tf           # exported values (CF domain, ARNs, …)
├── modules/             # reusable building blocks
│   ├── dynamoDB/
│   ├── lambda/
│   └── static_site_cf/
├── S3/                  # CloudFormation template + website assets
├── lambda_func/         # Python handler source
├── scripts/             # helper shell scripts (deploy & cleanup)
└── monitoring.tf        # CloudWatch alarms

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Prerequisites

• Terraform >= 1.3
• AWS CLI configured with credentials that can create IAM roles, Lambda, S3, CloudFront, and DynamoDB
• A registered domain in Route 53 (optional – for a custom vanity host)

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Quick Start

# 1) Initialise providers & modules
terraform init

# 2) See what will be created
terraform plan -out tfplan

# 3) Launch the stack
terraform apply tfplan

# 4) Upload/Invalidate assets (runs automatically via null_resource, but you can force):
./scripts/deploy_assets.sh

After ~10 minutes, Terraform exports the CloudFront URL. Browse to it and shorten your first link:

curl -i "https://<cloudfront-domain>/abc123"

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Clean Up

terraform destroy

The destroy phase empties the S3 bucket versions first (via scripts/empty_bucket.sh) to avoid the classic "bucket not empty" error.

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Cost Footprint (us‑east‑1, 1 M hits/month)

Component	Monthly Cost (USD)
S3 Storage	< 0.10
CloudFront	~ 2.50
Lambda (128 MB)	~ 0.20
DynamoDB (1 WCUs, 1 RCUs)	< 0.25
Total	≈ 3 USD

Costs scale linearly with traffic; staying well within AWS Free Tier for small projects.

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Extending the Stack

• Custom Domain + HTTPS

  • Add a aws_route53_record for @ and www → CloudFront domain.
  • Request an ACM certificate in us‑east‑1 (required by CloudFront) and attach it via the static_site_cf module.

• CI/CD

  • Replace null_resource.upload_assets with a GitHub Actions workflow that runs aws s3 sync + aws cloudfront create-invalidation on main branch pushes.

• Analytics

  • Stream CloudFront access logs to S3 and query with Athena.

• Authentication

  • Swap Lambda for an API Gateway + Cognito authorizer if you need per‑user quotas.

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Troubleshooting

Symptom	Fix
403 Forbidden on assets	Check that OAI is attached and S3 public access is blocked correctly. Re‑run deploy_assets.sh if paths changed.
502/504 on short URL hits	Verify Lambda URL endpoint is in the origins list of CloudFront and health checks pass.
Terraform destroy fails on S3	Ensure all object versions are purged; the provided empty_bucket.sh handles versioned buckets.

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Acknowledgements

Made with 💻 Terraform, ☁️ AWS, and a healthy dose of curiosity.