The 12-Factor App is a set of best practices for building modern, scalable, and maintainable cloud-native applications. It was introduced by Heroku to help developers build software that is portable, resilient, and easy to deploy. Here’s a quick overview of the 12 factors:

1. Codebase

One codebase per application, tracked in version control (e.g., Git), with multiple deployments (dev, staging, prod).

2. Dependencies

Explicitly declare dependencies in a package manager (e.g., requirements.txt for Python, package.json for Node.js).

3. Config

Store configuration (e.g., database URLs, API keys) in environment variables, not in code.

4. Backing Services

Treat databases, caches, and message queues as attached resources that can be swapped easily.

5. Build, Release, Run

Separate the build (compiling code), release (config + build), and run (execution) stages.

6. Processes

The app should be stateless, meaning it doesn’t store session data on the server (use a database or cache instead).

7. Port Binding

The app should be self-contained and expose services via a port (e.g., using localhost:5000 instead of a hardcoded address).

8. Concurrency

Scale out by running multiple stateless processes instead of large monolithic instances.

9. Disposability

Apps should be resilient and able to start/stop quickly to handle failures and deployments efficiently.

10. Dev/Prod Parity

Keep development, staging, and production environments as similar as possible to reduce issues when deploying.

11. Logs

Treat logs as event streams and send them to a logging system like ELK Stack, Splunk, or Fluentd instead of storing them in files.

12. Admin Processes

Run one-time admin tasks (e.g., database migrations, cron jobs) separately from the main application processes.

Why is the 12-Factor App Important?

✅ Cloud-native: Designed for microservices and containerized environments like Kubernetes
✅ Scalable: Easily scales with demand
✅ Portable: Can be deployed on different platforms (AWS, Azure, GCP, etc.)
✅ Maintainable: Reduces tech debt and makes debugging easier

The 12-Factor App