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Critical Flow — Commit to Signed Artefact

Sixteen messages. The important one is the second-to-last: the job reports, the attestor signs.

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Source control Admission Scheduler Sandbox mgr microVM job Secret broker Attestor Artefact store 1. push event (signed) 2. compile, classify trust 3. run admitted 4. fair-queue, lease job 5. assign job + lease 6. claim warm microVM 7. request scoped token 8. job-scoped, expiring 9. build and test 10. upload by digest 11. report outcome 12. observed inputs + digest 13. sign + log provenance 14. job sealed 15. destroy sandbox 16. lease expired, re-dispatch Critical Flow — Commit to Signed Artefact The job reports its outcome; the attestor signs it. A job can produce a bad artefact but never a credible claim about one. v 1.0 · owner Platform Engineering · date 2026-09

The ordering that matters

  • The sandbox uploads the artefact and reports its outcome. The attestor then signs from the inputs the platform observed. Provenance therefore records what the platform saw, not what the build said about itself.
  • The credential is requested by the job and issued by the broker against a job-scoped token. Nothing long-lived is ever present in the sandbox to be stolen.
  • Destroying the sandbox is the last step, and it is asynchronous: the result is already sealed, so teardown cannot fail a successful job.

The failure branch

  • The red message is lease expiry. A runner that goes silent is detected by its lease, not by the absence of a report, and the job is re-dispatched.
  • A job is never reported successful on the basis of an absent runner. That rule is what makes a partition resolve to re-dispatch rather than to a false green.

Assumptions

  • Queued to first step p50 ≤ 8 s, p99 ≤ 60 s; 12,000 sandbox creations per minute at peak.
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Solution Architecture v1.0 · Amazon Web Services · Platform Architecture · 2026-0913-job-dispatch-sequence