The Twelve Factors

Immutable (infrastructure), Ephemeral, Declarative, Automated Applications

The Twelve Factors provides guidelines on how to implement cloud aware applications.

Deployment/build process factors:

Factor	Description
Codebase	One repository for each application
Dependencies	Explicitly declare all dependencies. Do not rely on implicit System-wide packages
Config	Things that changes between environments should be separated from the code
Backing services	Attachable resources via a single URL
Build, release, run	Run with one line (e.g. using a script)

Application Architecture related factors:

Factor	Description
Processes	Processes should be stateless. Do not use stick sessions
Port Binding	Should be done by the applications: binding should not relay on external infrastructure
Concurrency	Scaling up and scaling out using different processes
Disposable	Quick startup, Resilience to failures, graceful shutdown
Dev/Prod Parity	dev = stag = prod
Logs	Logs should be thread as events not like files. Log everything on the same channel
Admin Processes	Run as isolated processes. This is similar to scaling a new container which is isolated from the prod processes

Extra link

• https://12factor.net/

• https://www.youtube.com/watch?v=94PxlbuizCU