Container Registry and Software Supply Chain Platform  ·  View 03 of 33  ·  1 · Context and scope

The Four Planes

Why the boundary between the artifact plane and the evidence plane is the load-bearing seam of the whole system.

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Artifact plane — bytes, never verdicts Registry services Harbor Core auth · quota · GC Distribution OCI dist v2 Proxy Cache per region Artifact storage MinIO Blob Store content addressed Metadata Store PostgreSQL · regional Evidence plane — the system of record Authoritative Attestation Store append-only DSSE Rekor Log inclusion proofs Fulcio CA 10 min certs Derived and rebuildable Component Index rebuild ≤ 4 h Findings Store history kept 3 y Policy plane — versioned, reviewed data Authoring and build Policy Repository Rego in Git Bundle Builder opa build · signed Registers and rehearsal Exception Registry Suppression Registry Dry-Run Engine last 24 h traffic Enforcement plane — one per cluster In-cluster Admission Controller OPA embedded Local Bundle Cache max stale 30 min Local Evidence Cache BoltDB Build Pipelines Tekton Workload Clusters kubelet pulls blobs push by digest artifact event evidence feed bundle poll allow / deny blob pull The Four Planes and the Load-Bearing Seam Interface / broker Data store Security / platform External / third party Application we own synchronous event / async batch The registry may be unavailable without the platform losing its ability to decide. v 1.0 · owner Enterprise Architecture · date 2026-09

The critical design decision

  • The registry stores evidence; it never stores a verdict
  • Every alternative collapses into a stored boolean that was true when written and decays silently afterwards
  • The consequence: a policy evaluation sits on the critical path of every pod start, which forces the caching in act 5 and the degraded modes in act 6

What the separation buys

  • The registry may be unavailable without the platform losing its ability to decide
  • The evidence plane may be authoritative without ever serving a byte of an image
  • Revocation becomes a real mechanism: an artifact's verdict changes without the artifact changing

What it costs

  • Evidence must reach every enforcement point, and staleness becomes a first-class concern
  • Two stores to operate and back up rather than one
  • A verdict that changed after admission does not evict the running pod — a separate mechanism, deferred to phase 3
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Solution Architecture v1.0 · Data & AI Global Practice · 2026-09 · 33 views · open-source, on-premises03-four-planes