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deploy-stack

Ephemeral PR Previews

When enabled, deploy-stack automatically configures your GitHub Actions pipeline to spin up isolated, temporary AWS environments every time a developer opens a Pull Request.

A bot will comment on the PR with a live URL (e.g., http://pr-123-your-app...), allowing your team to test features, UI changes, and API updates before merging to main. When the PR is closed or merged, the environment is automatically destroyed.

🏗️ How it Works

Section titled “🏗️ How it Works”

Under the hood, deploy-stack utilizes Terraform Workspaces.

When a PR is opened, Terraform creates a new workspace (e.g., pr-12). It provisions a completely isolated Application Load Balancer and ECS Fargate Task using the exact same infrastructure definitions as your production environment, ensuring 100% parity.

To save time and simplify architecture, PR environments share your production AWS Secrets Manager vault and ECR Image Repository.

⚖️ The Rule of Thumb: Should I enable this?

Section titled “⚖️ The Rule of Thumb: Should I enable this?”

✅ Enable PR Previews if:

  • You are working on a team of 2+ developers and require visual QA or UX sign-off before merging code.
  • You are building a frontend application or full-stack monolith where seeing the live UI is critical.

❌ Do NOT enable PR Previews if:

  • You are a solo developer (you can just test locally).
  • You have a massive volume of PRs (e.g., automated Dependabot updates). Spinning up an AWS Load Balancer takes ~3 minutes, which will slow down rapid automated merges.

💰 AWS Cost Implications

Section titled “💰 AWS Cost Implications”

Because PR previews provision a real Application Load Balancer (ALB) and ECS Fargate compute tasks, they are not free.

  • Compute: You are charged standard AWS Fargate rates per minute while the PR environment is running.
  • Load Balancing: AWS charges $16/month per active Load Balancer. If a PR is open for 2 days, you pay the prorated ALB cost for those 48 hours ($1.00).

To keep costs low, ensure your team closes or merges Pull Requests promptly so the teardown.yml workflow can destroy the resources and stop the billing clock!