What is the difference between Docker and Docker Compose?

Docker is used to build and run a single container. Docker Compose is a tool for defining and running multi-container applications, such as an app that needs a PostgreSQL database and a Redis cache to function.

How do I handle persistent data in Docker Compose?

Use 'Volumes'. Volumes allow you to map a folder on your host machine to a folder inside the container. This ensures your database data persists even if the container is destroyed.

Can I use Docker Compose for production?

While possible for small apps, production environments usually require more robust orchestrators like Kubernetes. Docker Compose is primarily designed for development, testing, and simple staging environments.

Docker Compose for Node.js: Orchestrating Development Environments

Docker Compose Key Concepts

01. Healthchecks (Ready states)
02. Extends (DRY config)
03. Bridge Networks (Isolation)
04. Performance (VirtioFS)

The "It Works on My Machine" era is over. Professional backend development requires an environment that is reproducible, scalable, and isolated. Docker Compose allows you to define your entire Node.js infrastructure in a single YAML file, ensuring that your team is running identical versions of every dependency.

1. Advanced Orchestration: Healthchecks and Readiness

A common Docker failure is when the Node.js container starts faster than the PostgreSQL database, leading to a "Connection Refused" crash. The Pro Fix: Use Healthchecks. Instead of just depends_on, tell Compose to wait until the database is actually "Healthy" before starting the app.

// Reliable Service Startup

db:
image: postgres:15-alpine
healthcheck:
test: ["CMD-SHELL", "pg_isready -U postgres"]
interval: 5s
timeout: 5s
retries: 5

app:
build: .
depends_on:
db:
condition: service_healthy

2. Multi-Stage Compose: dev.yml vs test.yml

Don't clutter your main Compose file with testing tools. Use the extends keyword or multiple file flags (-f) to layer configurations.

base.yml: Shared image definitions and networks.
dev.yml: Adds bind-mounts for hot reloading and exposes debug ports.
test.yml: Spins up a clean database and runs npm test then exits.

3. Volume Performance on Mac/Windows

If your `node_modules` are bind-mounted on macOS, your app will be 10x slower because of the filesystem translation layer. The Fix: Use VirtioFS (in Docker Desktop settings) or Named Volumes for your `node_modules`. This keeps the heavy I/O operations inside the Linux VM while still allowing you to edit source code on your host machine.

4. Internal DNS and Networking Bridges

Docker Compose automatically creates a Bridge Network for your project. This provides an internal DNS. Your Node.js app can connect to http://redis:6379. Security Tip: Use the internal: true flag for your database network. This prevents your DB from being accessible even via localhost, forcing all access to go through your application container.

5. Pro Pattern: The "Clean Room" CLI

Avoid installing tools like migrate or redis-cli on your host. Use Compose as a runner:

// Run one-off commands in your stack

docker-compose run --rm app npm run migrate

This ensures that even your management commands run in the exact environment they are designed for.

Conclusion

Docker Compose is the bridge between writing code and shipping systems. It removes the complexity of local setup and ensures that your development cycle is fast, stable, and production-aligned. A single YAML file is all that stands between a messy installation and a professional engineering workspace.