Immutable Infrastructure
Immutable infrastructure is an operating model where you replace production resources with newly built versions instead of changing them in place. It makes each deployed version repeatable, testable, and easier to compare with its source definition.
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Intro
Immutable Infrastructure
Immutable infrastructure changes how you maintain production systems. You do not patch, reconfigure, or repair a running resource in place. You build a replacement, test it, deploy it, and retire the old resource.
“Immutable” describes the operating rule after deployment. It does not mean the system never changes. The system changes through replacement.
Why replacement changes operations
An in-place change starts with a running resource and alters its state. Over time, manual fixes, partial updates, and repeated configuration runs can make nominally identical resources behave differently. That difference is configuration drift.
Replacement starts from a version-controlled definition or image. The delivery pipeline builds the candidate and applies the same checks each time. Production receives the tested candidate rather than a sequence of repair actions.
This model gives you a clearer answer to a basic incident question: “What is running?” The deployed version points back to a build input and its test evidence. You can compare versions instead of reconstructing a server’s change history.
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Sources
- https://martinfowler.com/bliki/ImmutableServer.html
Supports
- Immutable servers are replaced rather than modified after deployment
- Base-image changes are tested before rollout
- Configuration should come from outside the server and remain limited
- Durable data and valuable logs require storage outside disposable compute
- Replacement suitability depends on rebuild speed and state boundaries
- https://docs.aws.amazon.com/wellarchitected/2023-10-03/framework/rel_tracking_change_management_immutable_infrastructure.html
Supports
- Immutable infrastructure disallows in-place production updates and deploys new resources
- Consistency, reproducibility, drift reduction, and recovery benefits
- Infrastructure as code and automation as implementation supports
- Canary and blue-green rollout behavior
- Drift detection and restricted modification of running resources
- https://docs.aws.amazon.com/prescriptive-guidance/latest/essential-eight-maturity/theme-2.html
Supports
- Approved secured pipelines as the route for infrastructure changes
- Restricted routine direct access and controlled break-glass access
- Repeatable machine-image and container-image builds
- Infrastructure as code, policy checks, scanning, and compliance monitoring
- Image-pipeline patch management
- https://developer.hashicorp.com/packer/docs
Supports
- Machine images built for multiple platforms from one source configuration
- Templates, validation, plugins, and image lifecycle management
- Golden images as a common organizational use case
- https://developer.hashicorp.com/packer/guides/packer-on-cicd
Supports
- Automated immutable image builds in a continuous delivery pipeline
- Image storage followed by provisioning new instances