Hey Devs,
There are many methodologies out there for building software, each suited to different stages or goals. One methodology that stands out for building robust, scalable, and maintainable applications—especially in cloud-native environments—is the 12 Factor App.
When starting a project, whether it’s an MVP or a full-fledged product, it’s crucial to have a clear plan—a foundation that sets the project up for long-term success. The 12 Factor methodology provides a practical checklist for structuring an application properly from day one. Regardless of the technology stack or framework you use, these principles help ensure your app is ready to scale and adapt over time.
1. Codebase
There should be one codebase tracked in version control (like GitHub, GitLab, Bitbucket), and many deployments. All environments—development, staging, production—should derive from a single source of truth.
🔁 “One app, one repo.”
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2. Dependencies
All external dependencies must be explicitly declared in manifest files (like package.json, pyproject.toml, etc.), and not assumed to be installed on the system.
📦 Use dependency managers (npm, yarn, pip) to install and isolate packages.
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3. Config
Configuration such as API keys, database URLs, and client secrets should be stored in environment variables, not hardcoded in the codebase. This allows easy configuration changes per environment (dev, staging, prod).
🔐 Environment-driven configuration keeps your app flexible and secure.
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4. Backing Services
Treat all services your app consumes—like databases, queues, caches, storage—as attached resources. They should be easily swappable without code changes, referenced via URLs or credentials.
🔄 Replace your database or S3 bucket without touching the code.
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5. Build, Release, Run
Separate the stages of:
• Build: Compile the code and install dependencies.
• Release: Combine the build with configuration for a specific environment.
• Run: Execute the app in the runtime.
🔧 This ensures predictable, repeatable deployments.
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6. Processes
Your application should run as stateless processes. Any data that needs to persist should be stored in a backing service (like a database or object storage).
☁️ Restarting your app should not affect its state or integrity.
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7. Port Binding
The app should self-host by binding to a port, and not rely on external servers (like Apache or Nginx) for communication.
🌐 For example, in Node.js: app.listen(process.env.PORT || 3000);
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8. Concurrency
Design your app to scale out by running multiple instances or processes for different tasks (e.g., web server, background worker, scheduler).
⚙️ Use process managers (PM2, Docker, Kubernetes) to scale horizontally.
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9. Disposability
Apps should start up and shut down quickly and gracefully, allowing for fast scaling and reliable deployments.
⏱️ Handle termination signals (like SIGTERM) to close resources cleanly.
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10. Dev/Prod Parity
Keep development, staging, and production environments as similar as possible to avoid bugs and deployment issues.
🐳 Tools like Docker are ideal to ensure environment parity.
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11. Logs
Treat logs as event streams. Your app should write logs to stdout/stderr, and let external tools (like ELK, Sentry, or Datadog) handle log aggregation and analysis.
📊 Don’t manage logs with files inside the app.
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12. Admin Processes
Administrative tasks like database migrations, data seeding, or one-time scripts should be run as isolated one-off processes.
🛠️ Example: npx prisma migrate deploy or rails db:migrate
Final Thoughts
The 12 Factor App methodology isn’t a strict rulebook—it’s a set of guiding principles that help you build better apps. Whether you’re working on a monolith, microservices, or serverless architecture, applying these concepts will significantly improve your application’s resilience, scalability, and maintainability.
