A cloud architect designs a server fleet so that once instances are deployed, they are never patched, reconfigured, or logged into directly. Any required update is implemented by building a new machine image with the change baked in and replacing the running instances entirely. Which principle is being applied?
- AIdempotency
- BBlue-green deployment
- CImmutable infrastructure
- DConfiguration drift prevention
Show answer & explanationAnswer & explanation
Correct answer: C. Immutable infrastructure
Immutable infrastructure means deployed instances are never modified in place; instead, changes are made by building a new image and replacing old instances, which eliminates configuration drift as a side effect. Blue-green deployment describes a traffic-cutover technique and could use immutable images, but the concept described—never modifying instances after deployment—is specifically immutable infrastructure, while idempotency and drift prevention describe related but distinct outcomes rather than this deployment philosophy itself.
Why the other options are wrong
- A. Idempotency means repeated operations yield the same result, not that instances are never modified.
- B. Blue-green deployment is a traffic-switching technique that may use immutable images but isn't the principle itself.
- D. Drift prevention is a benefit/goal, but the described practice itself is the immutable infrastructure principle.
Immutable Infrastructure
An infrastructure management approach where deployed servers/instances are never modified after creation; updates are made by deploying new images and replacing old instances.
- Eliminates configuration drift by design
- Relies on automated image building pipelines
- Often paired with blue-green or rolling deployment for cutover
Memory trick: Immutable = frozen statue; you don't repaint it, you cast a whole new one.