The Twelve-Factor App methodology is a methodology for building software as a service applications. These best practices are designed to enable applications to be built with portability and resilience when deployed to the web.

• Codebase – There should be exactly one codebase for a deployed service with the codebase being used for many deployments.
• Dependencies – All dependencies should be declared, with no implicit reliance on system tools or libraries.
• Config – Configuration that varies between deployments should be stored in the environment.
• Backing services All backing services are treated as attached resources and attached and detached by the execution environment.
• Build, release, run – The delivery pipeline should strictly consist of build, release, run.
• Processes – Applications should be deployed as one or more stateless processes with persisted data stored on a backing service.
• Port binding – Self-contained services should make themselves available to other services by specified ports.
• Concurrency – Concurrency is advocated by scaling individual processes.
• Disposability – Fast startup and shutdown are advocated for a more robust and resilient system.
• Dev/Prod parity – All environments should be as similar as possible.
• Logs – Applications should produce logs as event streams and leave the execution environment to aggregate.
• Admin Processes – Any needed admin tasks should be kept in source control and packaged with the application.