A deployment strategy that eliminates downtime by running two identical environments and switching traffic between them.
Blue-Green deployment is a strategy where you run two identical production environments (Blue and Green). One serves live traffic, the other is idle. When deploying, you update the idle environment and switch traffic to it.
Think of it like having two identical stages. While the band plays on Stage 1 (Blue), set up Stage 2 (Green). When ready, switch the audience to Stage 2. No interruption.
Blue Environment: Currently running production. Serving live traffic.
Green Environment: Identical copy. Deploy new version here.
Switch: Once Green is ready and tested, route all traffic to it.
Blue Becomes Standby: Keep Blue running briefly in case you need to rollback.
Zero Downtime: Users never experience service interruption.
Instant Rollback: Problems? Switch back to Blue in seconds.
Testing in Production: Test new version with production data before switching traffic.
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Safe Deployments: Confidence that you can quickly revert if needed.
Cost: Running two environments doubles infrastructure costs (temporarily).
Database Migrations: Complex when schema changes. Both versions must work with same database.
State Management: Sessions, caches must work across environments.
Resource Intensive: Need double the servers during deployment.
Rolling Deployment: Gradually update servers one at a time. Slower but uses less resources.
Canary Deployment: Route small percentage of traffic to new version first. Safer but more complex.
Blue-Green: Instant full switch. Safest but most expensive.
Netflix: Uses variations of blue-green for their massive deployments.
Amazon: Blue-green deployments for many services to maintain uptime.
E-commerce Sites: Use blue-green during high-traffic periods (Black Friday) when downtime is unacceptable.
Cloud Platforms: AWS Elastic Beanstalk, Google Cloud, Azure support blue-green natively.
Kubernetes: Blue-green with multiple deployments and service switching.
Load Balancers: Configure to switch between environment groups.
Critical Systems: Banking, e-commerce, healthcare where downtime costs money or safety.
Frequent Deployments: Teams deploying multiple times daily.
Rollback Safety: When ability to instantly revert is crucial.
Limited Resources: Cannot afford double infrastructure.
Stateful Apps: Complex state makes switching difficult.
Small Apps: Overkill for low-traffic applications.
Backward Compatible Migrations: New code must work with old schema. Old code must work with new schema.
Separate Data Migrations: Run schema changes before or after deployment, not during.
Read-Only Period: Brief read-only mode during switch if needed.
Blue-Green deployment is the gold standard for zero-downtime deployments. It costs more but provides ultimate safety and instant rollback capability.
For critical production systems where downtime is unacceptable, blue-green deployment is worth the investment.
