Golden image
A pre-built, pre-configured, and hardened template image (for a VM or container) that all instances are started from. Instead of installing and configuring each new server from scratch, you "bake" everything into a golden image once and clone it.
Mechanic: you build the image once (the "bake" step, often with tools like Packer) with the OS, patches, agents, security hardening, and base config already in place, and then start all instances from it. Wins: fast start (nothing to install at boot — just start), consistency (all instances identical, from the same tested template), and security (the hardening is built in and reviewed). It's the prerequisite for immutable infrastructure (on a change you build a NEW golden image and replace, rather than patching running instances). Trade-off: you must regularly rebuild the image to get security patches in ("image freshness"), otherwise the security drifts. Examples: an AWS AMI, a hardened container base image. Related to immutable infrastructure and image digest.