Rollouts
Canary, blue/green, phased, shadow: choosing safety on purpose
Deploying isn’t one button. It’s a strategy.
Rollouts exist because production is not a lab.
Four rollout strategies (human definitions)
Canary
Send a small % of users/traffic to the new version first.
Good when you want early signal
Great with strong monitoring
Phased rollout
Ramp exposure gradually (10% → 25% → 50% → 100%).
Good default for user-facing features
Blue/Green
Two environments: old (blue) and new (green). Flip traffic when ready.
Great when you need fast cutover + fast rollback
Costs more infra
Shadow (traffic mirroring)
Copy real traffic to the new system but don’t serve its responses.
Great for validating performance/behavior
Doesn’t fully validate user experience
The “what should we use?” rule of thumb
Need safest cutover? Blue/green
Need early warning signals? Canary
Need steady control? Phased rollout
Need reality testing without user impact? Shadow
The metric question (the one that matters)
Before any rollout: define success/failure signals.
Error rate
Latency (p95/p99)
SLO burn
Business metrics (checkout conversion, drop-offs)
Rollouts without metrics are vibes.
Cheat sheet
Canary = small slice first
Phased rollout = gradual ramp
Blue/green = flip traffic between two stacks
Shadow = mirror traffic without serving responses
Next: Rollback vs Revert — and how to communicate during incidents.