@Ajit5ingh

Blue-Green vs Canary

Two powerful deployment strategies for zero downtime

What are Blue-Green and Canary Deployments?

Both are deployment strategies that help you release software updates without downtime. Blue-Green switches all traffic instantly between two identical environments. Canary gradually rolls out changes to a small percentage of users first.

How They Work

Blue-Green Deployment

The Concept: You have two identical production environments - Blue (current) and Green (new). When deploying, you switch all traffic from Blue to Green instantly.

How it works: You deploy your new version to the Green environment, test it thoroughly, then switch your load balancer to point all traffic to Green. The old Blue environment stays running as a backup.

Result: Instant switch - either all users get the new version or all users get the old version.

Canary Deployment

The Concept: You deploy the new version alongside the old one and gradually shift traffic. Start with 5% of users, then 25%, 50%, and finally 100%.

How it works: You run both old and new versions at the same time. Your load balancer routes a small percentage of traffic to the new version while monitoring metrics. If everything looks good, you gradually increase the percentage until all traffic goes to the new version.

Result: Gradual rollout - you can catch issues early and limit the impact on users. Perfect for testing new features with real user behavior.

Deployment Strategy Comparison


graph LR
  A[New Version] --> B{Strategy?}
  
  B -->|Blue-Green| C[Deploy to Green]
  C --> D[Test Green]
  D --> E[Switch All Traffic]
  E --> F[Done ✓]
  
  B -->|Canary| G[Deploy Canary]
  G --> H[5% Traffic]
  H --> I[25% Traffic]
  I --> J[100% Traffic]
  J --> F
  
  style A fill:#f1f5f9,stroke:#64748b,stroke-width:2px
  style B fill:#e0f2fe,stroke:#0284c7,stroke-width:2px
  style C fill:#e0f2fe,stroke:#0ea5e9,stroke-width:2px
  style D fill:#e0f2fe,stroke:#0ea5e9,stroke-width:2px
  style E fill:#e0f2fe,stroke:#0ea5e9,stroke-width:2px
  style G fill:#fef3c7,stroke:#f59e0b,stroke-width:2px
  style H fill:#fef3c7,stroke:#f59e0b,stroke-width:2px
  style I fill:#fef3c7,stroke:#f59e0b,stroke-width:2px
  style J fill:#fef3c7,stroke:#f59e0b,stroke-width:2px
  style F fill:#dcfce7,stroke:#16a34a,stroke-width:2px

Quick Comparison

Aspect	Blue-Green	Canary
Deployment Speed	Instant switch	Gradual rollout (hours/days)
Risk Level	Higher - all users affected immediately	Lower - limited user impact
Resource Usage	2x production resources needed	Slightly more than 1x resources
Rollback Time	Very fast (switch back)	Fast (stop routing new traffic)
Testing in Production	All users test at once	Real users test gradually
Complexity	Simple concept, complex infrastructure	Complex traffic management
Best For	Well-tested features, major releases	New features, experimental changes