What is Immutable Infrastructure?
An approach where servers are never modified after deployment — changes require building and deploying entirely new server instances.
With immutable infrastructure, servers are replaced rather than updated. New code or configuration changes mean building a new image, deploying new instances, and destroying old ones. This eliminates configuration drift and "snowflake" servers.
Benefits include consistency (every server is identical), easy rollback (deploy previous image), and reproducibility. Technologies include machine images (AMIs), containers (Docker), and infrastructure as code. Combined with blue-green deployments for zero-downtime updates.