The part someone else made

Its third row is the harbour’s supply chain: source, build, image, registry, deploy, and at every hop a chance to slip something in or to check that nobody did. This lesson walks that row one hop at a time.

Before you start. The Assembly Line (CI/CD) gave you the image, a sealed copy of the app and everything it needs, and two ways to name it: a tag, which is a movable label like 1.1, and a digest, the fingerprint of the exact bytes, which can never point at anything else. Application Hardening gave you the CVE, a public id for one known hole in one piece of software, and Least Privilege & the 12-Factor App gave you the habit of giving each part only the access it needs.