Interview Web App

A simple TypeScript web application that returns "Hello World". This app is containerised and ready for deployment.

Features

TypeScript-based Express web server
Returns "Hello World" on the root endpoint
Health check endpoint at /health
Docker containerization
Jest testing suite

Prerequisites

Node.js 20+ (for local development)
Docker and Docker Compose (for containerised deployment)

Installation

Install dependencies:

npm install

Development

Run the app locally in development mode:

npm run dev

The server will start on http://localhost:3000

Build

Compile TypeScript to JavaScript:

npm run build

Run the compiled version:

npm start

Testing

Run tests:

npm test

Generate coverage report:

npm run test:coverage

Docker

Build the Docker image

docker build -t interview-webapp .

Run the container

docker run -p 3000:3000 interview-webapp

Using Docker Compose

For local testing with Docker Compose:

docker-compose up

Endpoints

GET / - Returns "Hello World"
GET /health - Returns health status JSON: {"status": "ok"}

Testing the Application

Once running, test the endpoints:

# Test Hello World endpoint
curl http://localhost:3000/

# Test health endpoint
curl http://localhost:3000/health

Project Structure

.
├── src/
│   ├── app.ts           # Express app configuration
│   ├── index.ts         # Entry point
│   └── app.test.ts      # Jest tests
├── dist/                # Compiled JavaScript (generated)
├── coverage/            # Test coverage reports (generated)
├── Dockerfile           # Docker configuration
├── docker-compose.yml   # Docker Compose configuration
├── tsconfig.json        # TypeScript configuration
├── jest.config.js       # Jest configuration
├── package.json         # Dependencies and scripts
└── README.md            # This file

Interview Tasks

The following tasks should be completed as a take-home assignment. Allocate 30-60 minutes to complete the task. You will have access to this codebase the day before your interview to implement CI/CD workflows using GitHub Actions. Feel free to fork this repo generate a CI/CD in your forks GitHub actions, alternatively you could use tools like excalidraw to generate diagrams, write the yaml files, or use pseudo code.

Task 1: Continuous Integration (CI) Workflow

Requirement: Every change must pass continuous integration checks before making its way to the master branch.

CI Must Verify:

The TypeScript application compiles successfully
All tests pass
The Docker image can be built successfully

Points for discussion:

What events should trigger CI? (push to feature branches, pull requests, etc.)
How can you optimize build times?
What information should developers see when CI fails?

Task 2: Continuous Deployment (CD) Workflow

Requirement: Changes merged to master should be deployed automatically to production.

CD Must Include:

Deploy the application (you can mock this step with docker, or use pseudo code)
Post-deployment verification:
- Verify the health check endpoint returns 200 status
Notification when deployment or verification fails
- These notifications don't need to go anywhere real, printing to stdout is fine

Points for discussion: In a busy team repository with many daily commits to master, you need to consider:

Deployment Triggers: How do you handle high-frequency commits? Should every commit trigger deployment?
Concurrent Deployments: How do you handle multiple deployments triggered in quick succession?
Rollback Strategy: If smoke tests fail, how do you handle rollback? How would you ensure a rollback reverts to exactly the previous deployment state rather than rebuilding an older commit?
Environment Management: How would you extend this to handle different environments (staging vs production)?

linz/devops-interview