What is a Twelve Factor Compliant App

Today, building software-as-a-service (SAAS) has become a common practice for web applications. The twelve-factor compliant is a methodology to build modern SAAS applications. The twelve-factor methodology does not related to any specific technology, language, or platform.

Here is a list of the 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 

Learn more about the twelve-factor app here: http://12factor.net/

References:

http://12factor.net/