The Twelve-Factor App is a must read if you are writing software as a service

This is a really powerful article. Boils down to 12 principle the best practices for building scalable, testable and reliable web apps. The goals are in the introduction but are worth repeating:

• Use declarative formats for setup automation, to minimize time and cost for new developers joining the project;
• Have a clean contract with the underlying operating system, offering maximum portability between execution environments;
• Are suitable for deployment on modern cloud platforms, obviating the need for servers and systems administration;
• Minimize divergence between development and production, enabling continuous deployment for maximum agility;
• And can scale up without significant changes to tooling, architecture, or development practices.

Read the full article here: http://www.12factor.net/