Definition
Immutable infrastructure is a cloud computing approach where servers are never modified after they are deployed. Instead of updating existing systems, new instances are provisioned with the desired changes and the old ones are discarded. This methodology enhances system reliability and predictability by eliminating configuration drift and reducing the risk of introducing errors through manual updates. For instance, when deploying a new application version, you would build a new server image, deploy it, and then switch traffic to the new servers, rather than patching the existing ones. This contrasts with mutable infrastructure, where servers are routinely updated in place. Understanding immutable infrastructure is crucial for designing robust cloud environments and is frequently tested on AWS certification exams like the Solutions Architect Associate.