Theory

Updated

October 30, 2026

Theory: Progressive Delivery is Reducing Blast Radius Over Time

Kubernetes RollingUpdate is maxUnavailable/maxSurge, not traffic-aware. Canary and blue-green split traffic or replicas and add pause/analysis gates.

Invariants

  1. A Rollout replaces a Deployment as the object that owns ReplicaSets.
  2. Canary: some users (or pods) see the new version first.
  3. Blue-green: two full stacks; cut traffic when ready.
RollingUpdate   gradual pods, mixed traffic
Canary          gated traffic/replicas
Blue-green      two stacks, one cutover

What can break

  • Calling a 50% RollingUpdate a canary (no analysis, no traffic split).

How to read this chapter

Beyond RollingUpdate, canary/blue-green, risk.