A3. Consider deployed instances of infrastructure to be immutable

If you’re patching, maintaining, or modifying an instance of infrastructure, it’s becoming more like a “pet” than “cattle”. It is recommended that infrastructure instances be replaced, rather than modified in production. This means that the definition of an infrastructure component is what gets updated, not the component itself, and then a running infrastructure component is replaced with an updated version. This aligns well with the DevOps pattern. The Division should aim to make software development and systems engineering practices that facilitate the delivery of services through immutable infrastructure easy, and preferable to in-place patching and updates.