Theory

Updated

October 30, 2026

Theory: Blue-Green is Two Stacks and One Cutover

Active and preview Services point at old vs new ReplicaSets. Promotion swaps who is active. Analysis can run on preview before the swap.

Invariants

  1. Capacity is ~2× during the preview window.
  2. Rollback is swapping Services back, not a Git revert alone (Git should still record the desired Rollout spec).
  3. StatefulSets are a later limitation chapter.
Service active  →  RS blue
Service preview →  RS green     promote: swap active

What can break

  • Preview service accidentally public without auth.

How to read this chapter

Services, analysis, promote/rollback.