The 12-factor methodology is a set of best practices for building software-as-a-service (SaaS) applications that are:

Build for scale from the start

Use declarative format for setup and deploy

Strictly separate build and run stages

Export services via port binding

Use a dependency injection

Store config in the environment

Treat logs as event streams

Run as a single process

Disposability

Maximize robustness with fast startup and graceful shutdown

Keep development, staging, and production as similar as possible

Treat backing services as attached resources 

https://12factor.net/