Docker Compose for Local Dev

Docker Compose lets you define and run multi-container applications with a single YAML file.

Why Compose?

Real apps need more than one container: a web server, a database, a cache, maybe a queue. Compose wires them all together.

docker-compose.yml

yaml

version: '3.8'

services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      - DATABASE_URL=postgres://user:pass@db:5432/myapp
      - REDIS_URL=redis://cache:6379
    depends_on:
      - db
      - cache
    volumes:
      - .:/app          # Hot reload for development
      - /app/node_modules

  db:
    image: postgres:15-alpine
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: myapp
    volumes:
      - postgres_data:/var/lib/postgresql/data
    ports:
      - "5432:5432"

  cache:
    image: redis:7-alpine
    ports:
      - "6379:6379"

volumes:
  postgres_data:

Essential commands

bash

# Start all services
docker compose up -d

# See logs
docker compose logs -f app

# Stop everything
docker compose down

# Rebuild after Dockerfile changes
docker compose up --build

# Run a one-off command
docker compose exec app npm run migrate

Volumes

Named volumes (like postgres_data) persist data between container restarts. Your database won't lose data when you run docker compose down.

Bind mounts (like .:/app) sync your local files into the container — essential for hot-reload during development.