Understanding the Twelve-Factor App Methodology for SaaS in 2023

1. Codebase: Maintain One Source Code Repository

The first factor in the Twelve-Factor App methodology advocates for maintaining a single codebase for each application. This codebase is stored in a version control system, such as Git, and acts as the central source of truth for the application's entire lifecycle.

• Use a version control system to manage, track, and collaborate on changes in your codebase
• Maintain separate branches for staging and production environments, ensuring smooth deployments and clean code management
  

2. Dependencies: Declare and Isolate Explicitly

The second factor emphasizes the need for explicitly declaring and isolating an application's dependencies. This approach minimizes the likelihood of conflicts or issues arising from different versions of libraries, frameworks, or packages used in the application.

• Utilize package managers and dependency management tools (e.g., npm, Maven, or pip) to declare and manage dependencies
• Isolate dependencies in virtualized environments, such as virtual machines or containers, eliminating the risk of interference or collision with the system or other applications

3. Config: Separate Configuration from Code

The third factor outlines the importance of separating application configurations from the source code. This factor promotes seamless deployment of the application across different environments, as well as enhanced security, as sensitive data (e.g., API keys or database credentials) is not exposed within the code.

• Store configuration settings as environment variables or external configuration files, ensuring easy access and update without modifying source code
• Protect sensitive information by employing encryption or secret management solutions, such as HashiCorp Vault or AWS Secrets Manager

4. Backing Services: Treat as Attached Resources

The fourth factor highlights the need to treat backing services, such as databases, message queues, or caching systems, as attached resources that can be replaced or modified without impacting the application's core functionality.

• Use standardized interfaces and APIs to connect to backing services, enabling easy swapping or migration
• Configure connection information, such as URLs and credentials, as environment variables or separate configuration settings

5. Build, Release, Run: Separate Stages for a Robust Deployment Process

The fifth factor emphasizes the importance of separating the application's build, release, and run stages. This distinction ensures a more disciplined and consistent deployment process, minimizing the potential for errors or inconsistencies.

• Build stage: Compile the source code and produce an executable artifact (e.g., a binary, JAR file, or Docker image)
• Release stage: Combine the executable artifact with configuration settings for a specific environment (e.g., staging or production)
• Run stage: Deploy the release to the target environment and start the application

6. Processes: Execute as Stateless Services

The sixth factor outlines the need for applications to run as stateless processes. This approach ensures that the application can scale horizontally, as state and data are managed externally (e.g., by a database or distributed cache).

• Avoid storing application runtime state in local memory, opting for external backing services instead
• Ensure that instances of the application can be scaled and replaced independently, promoting flexibility and resilience

7. Port Binding: Expose Services via Port Binding

The seventh factor highlights the importance of exposing application services via port binding. This approach decouples the application from a specific runtime environment or third-party reverse proxy, allowing for easy deployment and migration between environments.

• Use a built-in web server or runtime environment to bind the application to a specific port, allowing other services or users to communicate via network requests
• Ensure the application follows the principles of a self-contained and independently-runnable service, eliminating dependencies on external systems

8. Concurrency: Use Process Model for Scalability

The eighth factor encourages applications to adopt the process model for better scalability. The process model advocates running multiple instances of an application or its components as separate processes, which can be independently scaled and managed.

• Identify functional components or units of work within the application that can be run as separate processes (e.g., workers or background jobs)
• Utilize specialized tools or services to manage and scale application processes, such as Kubernetes, AWS Lambda, or Celery