Aligning Azure App Configuration and Feature Flags with 12-Factor App Principles

Ronald Mariah · April 30, 2024

The 12-Factor App is a methodology for building software-as-a-service (SaaS) apps that emphasizes building scalable, flexible, and manageable applications. Developed by engineers at Heroku, this set of best practices is designed to enable applications to be deployed to the cloud with ease, reliability, and portability.

Here’s a brief overview of each of the twelve factors:

  • Codebase: One codebase tracked in revision control, many deploys. This means there should be exactly one codebase per app, with the codebase being used for many deployments.
  • Dependencies: Explicitly declare and isolate dependencies. The application should explicitly declare all dependencies, completely and exactly, via a dependency declaration manifest.
  • Config: Store config in the environment. Configuration that varies between deployments should be stored in the environment rather than in the code to keep the codebase clean from sensitive config data.
  • Backing Services: Treat backing services as attached resources. These services, like databases, messaging systems, and caching systems, are attached resources and should be accessible via a URL or other locator/credentials stored in the config.
  • Build, Release, Run: Strictly separate build and run stages. This involves maintaining strict separation between the build stage (where the code is converted into an executable bundle), the release stage (where the build is combined with the deployment’s current config), and the run stage (where the application runs in the execution environment).
  • Processes: Execute the app as one or more stateless processes. Any data that needs to persist must be stored in a stateful backing service, typically a database.
  • Port Binding: Export services via port binding. The application should be completely self-contained and should not rely on runtime injection of a webserver into the execution environment to create a web-facing service.
  • Concurrency: Scale out via the process model. The process model should be embraced for scaling applications, using the operating system’s process model where processes are first-class citizens.
  • Disposability: Maximize robustness with fast startup and graceful shutdown. The app’s processes should be designed for quick startup and graceful shutdown to maximize robustness with modern cloud platforms’ fast elastic scaling.
  • Dev/prod Parity: Keep development, staging, and production as similar as possible. This minimizes issues from environmental discrepancies and facilitates continuous deployment for maximum agility.
  • Logs: Treat logs as event streams. Logs should be treated as a continuous stream of events emitted by the service, captured by the execution environment, and routed to a final destination for viewing and long-term archival.
  • Admin Processes: Run admin/management tasks as one-off processes. These are done in an environment identical to the regular long-running processes of the app to avoid running administrative tasks against a different background.

Understanding the 12-Factor App Config Principle

The third principle of the 12-Factor App methodology focuses on config—storing configuration that varies between deployments outside of the code. This separation of config from code is fundamental because it lowers the risk of code changes between deployments and avoids the accidental upload of confidential config setups into version control.

Key Takeaways from the 12-Factor Config Principle:

  • Keep codebase clean of sensitive config data: Config data should not be included in the code repository.
  • Store config in the environment: Configuration that varies between deployments should be stored in the environment where the application runs.

How Azure App Configuration and Feature Flags Uphold the 12-Factor Principles

  • Separation of Config from Code: Azure App Configuration embodies the 12-Factor principle by serving as an external, centralized store for configuration data. By managing settings externally, it ensures that the application codebase remains free from sensitive config data, adhering to the guideline of strict separation between code and config.
  • Environment-Based Configurations: The service allows for dynamic handling of configurations across different environments (development, testing, production) without code changes. Each environment can have its own set of configurations managed through Azure App Configuration, simplifying the process of maintaining consistency across multiple deployments.
  • Dynamic Configuration without Service Restart: In line with the 12-Factor principles, Azure App Configuration enables dynamic configuration updates without needing to restart the application. This feature supports high availability and seamless updates in production environments, reflecting the 12-Factor’s emphasis on minimizing divergence between development and production. Integrating Feature Flags: A 12-Factor Approach

Feature flags take the concept of dynamic configurations further by allowing developers to toggle features on and off without deploying new code. This capability directly supports the 12-Factor method by enabling feature management at runtime, which is particularly useful for A/B testing, canary releases, and gradual feature rollouts.

Practical Steps to Implement Azure App Configuration and Feature Flags:

  • Set Up Azure App Configuration: Establish a dedicated store for configuration data, adhering to the principle of external configuration management.
  • Define and Manage Feature Flags: Use Azure App Configuration to define and manage feature flags, decoupling feature releases from code deployments.
  • Integrate with Applications: Utilize Azure SDKs to integrate configuration management into your applications without embedding config data in the codebase.


By leveraging Azure App Configuration and feature flags, developers can align with the 12-Factor App methodology, particularly the config principle, which is crucial for modern cloud-native applications. These tools not only enhance operational efficiency but also bolster the security and scalability of applications across various environments. For developers committed to following the 12-Factor guidelines, Azure provides a robust platform that supports best practices in software development.

For more detailed guidance on implementing these practices, refer to the Azure App Configuration documentation and explore how these tools can transform your application management strategies to be more in line with 12-Factor App principles.

Twitter, Facebook