Goal
Release changes without taking production down.
Patterns
Rolling
Update instances gradually. Simple, but can still cause partial outages.
Blue/Green
Two environments:
- blue = current
- green = new
Switch traffic when green is healthy.
Canary
Send 1%, then 10%, then 50% traffic to the new version while watching metrics.
What makes deployments safe
- readiness and liveness probes
- health checks before traffic switch
- fast rollback plan
- monitoring: error rate, latency, saturation
Rollback strategy
Always keep the previous known-good artifact available.
Exercise
Write a deployment checklist for your app:
- pre-checks
- deploy steps
- verification steps
- rollback steps
Next Step
Platform engineering: learn Kubernetes/GitOps so these patterns become standard.