What is the difference between blue-green and canary deployment?

Blue-green switches 100% of traffic at once between two environments. Canary gradually shifts traffic (1%, 5%, 25%, 100%) to the new version while monitoring metrics. Canary is more gradual; blue-green is all-or-nothing.

How do I handle database migrations with blue-green deployment?

Use the expand-contract pattern: first add new columns/tables (expand) that both old and new code can work with, deploy the new code, then remove old columns (contract) in a later release. Never make breaking schema changes in a single deployment.

Blue-Green Deployment Explained

Two identical environments, one switch — zero-downtime releases with instant rollback capability.

Blue-Green Deployment

Blue-green deployment is a release strategy that maintains two identical production environments — "blue" (current) and "green" (new). Traffic is switched from blue to green once the new version is validated, enabling zero-downtime releases and instant rollback by switching back.

Explanation

In a blue-green deployment, you maintain two production environments that are identical in infrastructure and configuration. At any time, one is "live" (receiving user traffic) and the other is "idle" (available for the next release). When deploying a new version, you deploy it to the idle environment, run smoke tests and validation, and then switch the load balancer or DNS to point traffic to the new environment. The old environment remains available for instant rollback. The key advantage is zero-downtime deployment — the switch is instantaneous from the user's perspective. If the new version has a critical issue, rollback is equally instant: just switch traffic back to the old environment. This dramatically reduces the risk of deployments compared to in-place updates where you modify the live environment directly. The main cost is infrastructure: you need two full production environments, which doubles your compute and infrastructure expenses. Database migrations add complexity — both environments must be compatible with the same database schema. This means database changes must be backward-compatible (additive only), and breaking schema changes require a multi-phase migration strategy.

Bookuvai Implementation

Bookuvai uses blue-green deployment for production releases in projects that require zero-downtime guarantees. Our infrastructure-as-code templates provision both environments automatically, and our CI/CD pipeline deploys to the idle environment, runs automated smoke tests, and switches traffic upon milestone approval. Database migrations follow an expand-contract pattern to maintain backward compatibility across both environments.

Key Facts

Zero-downtime deployments with instant rollback capability
Requires two identical production environments (higher infrastructure cost)
Database migrations must be backward-compatible for both environments

Related Terms

Frequently Asked Questions

What is the difference between blue-green and canary deployment?: Blue-green switches 100% of traffic at once between two environments. Canary gradually shifts traffic (1%, 5%, 25%, 100%) to the new version while monitoring metrics. Canary is more gradual; blue-green is all-or-nothing.
How do I handle database migrations with blue-green deployment?: Use the expand-contract pattern: first add new columns/tables (expand) that both old and new code can work with, deploy the new code, then remove old columns (contract) in a later release. Never make breaking schema changes in a single deployment.