Blue-Green Deployment
Blue-green deployment is a release strategy that runs two identical production environments — 'blue' (current) and 'green' (new) — and switches live traffic from one to the other once the new version is verified, enabling near-instant…
Definition
Blue-green deployment is a release strategy that runs two identical production environments — 'blue' (current) and 'green' (new) — and switches live traffic from one to the other once the new version is verified, enabling near-instant cutover and rollback.
Overview
In a blue-green deployment, the currently live version of an application (blue) keeps serving all production traffic while the new version (green) is deployed to a separate, identical environment. Once the green environment is deployed and verified — through automated tests, health checks, or a period of internal traffic — a router, load balancer, or DNS change redirects live traffic from blue to green, ideally with zero downtime for users. The key advantage is rollback speed: if a problem is discovered after cutover, traffic can be switched back to the still-running blue environment almost immediately, without needing to redeploy the previous version. The tradeoff is cost and complexity, since it requires maintaining two full production-capacity environments, at least temporarily, during the switch. Blue-green deployment is one of several strategies for reducing release risk, alongside canary deployment, which shifts traffic gradually rather than all at once, and rolling deployment, which replaces instances incrementally within a single environment. Feature-level risk can be managed separately with feature flags, which decouple releasing code from exposing functionality to users.
Key Concepts
- Two full, identical environments (blue and green) running in parallel
- Traffic cutover via load balancer, router, or DNS change
- Near-instant rollback by switching traffic back to the prior environment
- Reduced deployment downtime compared to in-place upgrades
- Higher infrastructure cost from running duplicate environments
- Often paired with automated health checks before cutover
Use Cases
Frequently Asked Questions
From the Blog
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