Blue-Green Deployment

What Is Blue-Green Deployment?

Blue-green deployment maintains two complete, identical production environments: Blue (current) and Green (new). When deploying, you update Green with the new version while Blue continues serving users. Once Green is tested and stable, you switch traffic to Green. If issues arise, you instantly switch back to Blue. This approach enables true zero-downtime deployments and easy rollbacks.

Blue-green deployment contrasts with rolling deployments (gradually replacing instances) and canary deployments (routing small traffic percentages to new version). Blue-green is ideal when you can't tolerate any errors—one switch, everything changes or nothing does. It's simpler conceptually than rolling deployments but requires double infrastructure capacity.

Blue-green requires careful attention to data migrations: if new versions require database schema changes, those must be backward-compatible so both Blue and Green can run. Deployment tools automate the traffic switch, making it instant and reliable. This approach is particularly valuable for AI systems where rollback must be instantaneous.