Glossary
Immutable Infrastructure
Immutable infrastructure is replaced entirely when a change is needed, rather than modified in place on a running system — a new instance is built from the updated definition and swapped in, and the old one is discarded rather than patched. This removes a specific class of risk that mutable infrastructure carries: an unauthorized or unintended change made directly to a running system, outside the normal deployment process, that then persists silently because nothing ever compares the running system back against what it was supposed to be.
With immutable infrastructure, that kind of drift becomes structurally harder to introduce and easier to notice, because every actual instance running at any given moment traces back to a specific, versioned definition rather than an accumulated, undocumented history of individual changes applied directly.