Summary · The outer delivery loop

Key takeaways

  • The outer delivery loop has four stages that begin exactly where the Sandcastle ends: review / PR, merge, GitOps delivery, and downstream Crossplane reconciliation.
  • The only artifact that crosses the boundary between the Sandcastle and the outer loop is the durable Git branch produced by the previous lesson’s hand-off. Everything the outer loop does is derived from that branch or supplied by the environment.
  • Three guardrails surround the outer loop and all live outside the Sandcastle boundary: automated verification and review attach to the PR, policy attaches at cluster admission before Crossplane sees the XR.
  • Cluster reconciliation remains Crossplane’s job. The outer loop hands the XR over once and does not try to short-circuit composition from the delivery side — the same rule the Hello Pico on Kubernetes lab already relies on in isolation.
  • The academy ships end-to-end runnable coverage of the whole picture. The Sandcastle → Kubernetes hand-off lab produces the XR at stage 0; the outer-delivery-loop lab drives stages 1–3 (real GitHub PR, real merge, GitOps sync via Flux or kubectl); and the Hello Pico on Kubernetes lab verifies stage 4 (Crossplane composes the Job). Stages 1–2 are runnable without a cluster; stages 3–4 add a Crossplane cluster (and optionally the flux CLI) as a documented prerequisite.

What comes next

  • Part 3 will continue with lessons on multi-artifact hand-offs and multi-environment promotion (dev → staging → prod), which build on the outer-loop shape this lesson pins down. See Part 3 for the current outline.
  • Downstream cluster verification of the composed artifact continues to live in labs/hello-pico-on-kubernetes/, the hand-off that seeds the outer loop lives in labs/handoff-sandcastle-to-kubernetes/, and the outer loop itself lives in labs/outer-delivery-loop/.
  • Policy tooling (OPA, Kyverno, Gatekeeper) is named here as a concrete example of the admission-time guardrail; a concrete policy demo is a reasonable extension exercise on top of this lab’s gitops-sync.sh.

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