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Mutable vs Immutable Infrastructure
Overview
Infrastructure can be classified as mutable or immutable, impacting security, maintainability, and reliability.
Mutable Infrastructure
Definition
- Can be modified after deployment.
- Updates, patches, and changes are applied in place.
- Common in traditional IT environments and on-premises setups.
Examples
- Updating a running server with patches.
- Changing configuration files manually.
- Using tools like Ansible, Chef, or Puppet to modify live systems.
Pros
- Flexibility to apply incremental changes.
- No need to redeploy the entire system for small updates.
- Works well in legacy environments.
Cons
- Higher risk of configuration drift.
- Harder to maintain consistency across environments.
- Security vulnerabilities can persist due to incomplete patching.
Immutable Infrastructure
Definition
- Once deployed, infrastructure is never changed.
- Updates require creating a new version and redeploying.
- Old versions are discarded and replaced with new instances.
Examples
- Deploying new container images instead of updating running containers.
- Using Infrastructure as Code (IaC) tools like Terraform or Pulumi.
- AWS AMIs, Kubernetes pods, and immutable storage models.
Pros
- Eliminates configuration drift, ensuring consistency.
- More secure: no ad-hoc changes that introduce vulnerabilities.
- Easier to rollback by reverting to a previous version.
- Works well in CI/CD environments with automation.
Cons
- Requires full redeployment for every change.
- Can be resource-intensive, requiring new instances instead of patches.
- Learning curve for teams used to mutable infrastructure.
Security Best Practices
- Prefer immutable infrastructure for better consistency and security.
- Use containerization and orchestration (e.g., Kubernetes) to enforce immutability.
- Automate deployments with Infrastructure as Code (IaC).
- Implement blue-green deployments to minimize downtime and risk.
- Regularly audit infrastructure to detect unauthorized changes.
References
- Infrastructure as Code: https://www.hashicorp.com/resources/infrastructure-as-code
- Kubernetes Best Practices: https://kubernetes.io/docs/setup/best-practices/
- AWS Immutable Infrastructure Guide: https://aws.amazon.com/builders-library/immutable-infrastructure/ ```