Deploying Web
Applications

Deployment is the process of making your application available to users on a server, not just on your machine.

For sites built with HTML/CSS/JS, React, Vue, Next.js (static export), etc. — no server needed.

For apps that need a backend server (Node, Python, Ruby, Go, etc.). PaaS handles infrastructure so you focus on code.

# Railway example
npm i -g @railway/cli
railway login
railway init
railway up   # deploys your app

The "big three" offer hundreds of services. Here are the ones relevant to web deployment.

DNS (Domain Name System) translates human-readable domain names into IP addresses that computers use.

HTTPS encrypts data between the browser and your server. It is required for modern web apps (browsers warn on HTTP).

# Using Certbot (most common)
sudo apt install certbot python3-certbot-nginx
sudo certbot --nginx -d myapp.com -d www.myapp.com

# Auto-renewal (runs twice daily)
sudo certbot renew --dry-run

Configuration that changes between environments (API keys, database URLs, feature flags) should never be hardcoded in your source code.

// WRONG: secrets in code
const dbUrl = "postgres://user:p4ssw0rd@db.com/prod";
const apiKey = "sk-abc123secret456";

// RIGHT: read from environment
const dbUrl = process.env.DATABASE_URL;
const apiKey = process.env.API_KEY;

# .env (add to .gitignore!)
DATABASE_URL=postgres://localhost/myapp
API_KEY=dev-test-key-12345
NODE_ENV=development

# Vercel
vercel env add DATABASE_URL

# Netlify
netlify env:set DATABASE_URL "postgres://..."

# Railway
railway variables set DATABASE_URL="..."

# Render: Dashboard → Environment tab

# AWS (Elastic Beanstalk)
eb setenv DATABASE_URL="postgres://..."

# Docker
docker run -e DATABASE_URL="..." myapp

A reverse proxy sits between users and your app server(s), handling HTTPS termination, load balancing, caching, and more.

server {
    listen 443 ssl;
    server_name myapp.com;

    ssl_certificate /etc/letsencrypt/live/myapp.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/myapp.com/privkey.pem;

    location / {
        proxy_pass http://localhost:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

# Caddyfile - that's it! Auto HTTPS.
myapp.com {
    reverse_proxy localhost:3000
}

How you roll out new code to production without causing downtime or breaking things for users.

Deploying is not "done" when the code is live. You need to know when things break and why.

// Use structured JSON logs, not console.log
const logger = require('pino')();

logger.info({ userId: 123, action: 'login' },
  'User logged in');

logger.error({ err, requestId: req.id },
  'Payment failed');

What it actually costs to host a web application at different scales.

Run through this before every production deploy.

A complete GitHub Actions workflow that builds, tests, containerizes, and deploys.

# .github/workflows/deploy.yml
name: Build & Deploy
on:
  push:
    branches: [main]

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with: { node-version: 20 }
      - run: npm ci
      - run: npm test
      - run: npm run build

  deploy:
    needs: test
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write
    steps:
      - uses: actions/checkout@v4
      - uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - uses: docker/build-push-action@v5
        with:
          push: true
          tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:latest
      # Deploy to your platform of choice:
      # - fly deploy
      # - railway up
      # - aws ecs update-service ...