Docker Compose concept

Docker Compose runs several containers together from one file, like your app plus a database. One command starts everything with the right settings and connections.

# docker-compose.yml
services:
  app:
    build: .
    ports:
      - "3000:3000"
    environment:
      DATABASE_URL: postgres://postgres:secret@db:5432/app
    depends_on:
      - db

  db:
    image: postgres:16
    environment:
      POSTGRES_PASSWORD: secret
      POSTGRES_DB: app

docker compose up -d   # start everything
docker compose down    # stop everything