Immutable Infrastructure is more important than Infrastructure as Code, fwiw. The latter just means "it's in [version controlled] code". This has a variety of

Immutable Infrastructure is more important than Infrastructure as Code, fwiw. The latter just means "it's in [version controlled] code". This has a variety of use cases, and it might mean you end up in a quagmire of complexity. It's become a cargo cult thing where I've seen people adopt horribly complex, fragile solutions over practical ones "because IaC". The former is a principle that basically has no downside, and only improves operational integrity. Even if you're literally deploying everything by clicking in the Console, it's still massively more reliable, repeatable, and recoverable as immutable artifacts. The next thing I'd recommend before investing heavily in IaC is auto-recovery. The most obvious example is Autoscaling Groups, but any health check combined with an automatic action such as restart or re-deploy can work. This works best with Immutable Infrastructure, and typically does not require IaC.