The Real Trade-offs
Blue-green deployments maintain two identical production environments. Traffic switches instantly after testing the new version. If something breaks, you flip back immediately. The problem: you're running double infrastructure at all times. One bank's platform team told us they keep blue-green for core banking systems despite the cost because instant rollback matters more than efficiency.
Canary deployments route 5-10% of traffic to the new version first. You monitor error rates and latency before expanding to 25%, then 50%, then 100%. Smaller blast radius, less infrastructure waste. The catch: you need proper monitoring. Without it, you're flying blind.
What Works in Production
Kubernetes makes both strategies easier than they used to be. Blue-green needs service routing configuration and double the pods. Canary needs traffic splitting (Istio or similar) and observability (Prometheus, Grafana). Health checks matter either way. Liveness probes restart broken containers. Readiness probes keep traffic away from containers that aren't ready. Get the timeouts wrong and your deployment fails for the wrong reasons.
Database migrations complicate both strategies. You can't run two schema versions simultaneously unless you plan for it. The pattern that works: make changes backward compatible. Add columns before removing old ones. Deploy in stages, not all at once.
The Kubernetes Context
Docker Swarm offered simpler rolling updates but fewer teams use it now. K3s makes canary deployments accessible for smaller teams without full Kubernetes complexity. Most production teams we talk to use rolling deployments for low-risk changes, canary for user-facing features, blue-green for infrastructure updates.
The monitoring piece is non-negotiable for canary deployments. Prometheus alerts should trigger on error rate spikes or latency increases. Grafana dashboards should show canary metrics versus stable version side by side. Without this visibility, canary deployments just slow down your bad deployments instead of catching them.
What Actually Matters
Resource cost versus risk reduction. Blue-green: high cost, instant rollback, simpler operations. Canary: medium cost, gradual validation, complex routing. Many teams use both depending on what they're deploying. The Friday 5 PM deployment becomes routine when the rollback plan is faster than the panic.