The twelve-factor app is a methodology for building software-as-a-service apps that:

• Use declarative formats for setup automation, to minimize time and cost for new developers joining the project;
• Have a clean contract with the underlying operating system, offering maximum portability between execution environments;
• Are suitable for deployment on modern cloud platforms, obviating the need for servers and systems administration;
• Minimize divergence between development and production, enabling continuous deployment for maximum agility;
• And can scale up without significant changes to tooling, architecture, or development practices.

Twelve Factors

1. Codebase: One codebase tracked in revision control, many deploys
2. Dependencies: Explicitly declare and isolate dependencies
3. Config: Store config in the environment
4. Backing services: Treat backing services as attached resources
5. Build, release, run: Strictly separate build and run stages
6. Processes: Execute the app as one or more stateless processes
7. Port binding: Export services via port binding
8. Concurrency: Scale out via the process model
9. Disposability: Maximize robustness with fast startup and graceful shutdown
10. Dev/prod parity: Keep development, staging, and production as similar as possible
11. Logs: Treat logs as event streams
12. Admin processes: Run admin/management tasks as one-off processes

References

• https://12factor.net/