12-Factor Application

Overview

The 12-Factor methodology defines practices for building cloud-ready applications with portability, repeatability, and operational consistency.

Core Factors in Practice

• Codebase: one tracked codebase per app
• Dependencies: explicitly declared and isolated
• Config: stored in environment variables
• Backing services: attached resources treated as replaceable
• Build, release, run: strictly separated stages

flowchart LR
    A[Build] --> B[Release]
    B --> C[Run]

Practical Example

A web API stores environment-specific settings outside source code.

# Development
setx DATABASE_URL "postgres://dev-db:5432/app"
setx REDIS_URL "redis://dev-cache:6379"

# Production pipeline
setx DATABASE_URL "postgres://prod-db:5432/app"
setx REDIS_URL "redis://prod-cache:6379"

var databaseUrl = Environment.GetEnvironmentVariable("DATABASE_URL");
var redisUrl = Environment.GetEnvironmentVariable("REDIS_URL");

Operational Benefits

• Predictable deployment across environments
• Reduced configuration drift
• Better alignment with container and Kubernetes workflows

Common Pitfalls

• Storing secrets in repository files
• Mixing build-time and runtime concerns
• Treating local scripts as production release process

Key Takeaways

• 12-Factor principles improve cloud portability and reliability.
• Environment-driven configuration is a foundational practice.
• Build-release-run separation supports controlled deployments.