Blue-green deployment vs rolling deployment: Choosing a deployment strategy

Blue-green and rolling deployments are two strategies for updating software systems, each with distinct advantages and challenges. Blue-green deployment involves maintaining two identical production environments, allowing for zero-downtime updates by switching user traffic instantly from the current environment to a newly updated one, which facilitates immediate rollback if necessary. This method is effective for minimizing risk and ensuring consistent user experiences but requires double the infrastructure resources and can be complex when managing stateful applications and database migrations. In contrast, rolling deployment updates software gradually across a server cluster, using existing infrastructure efficiently and reducing potential risks by affecting only a subset of users at any time. Although rolling deployments are more cost-effective and suitable for stateful applications, they take longer to complete, may lead to temporary mixed-version states, and have more complex rollback procedures compared to the instant rollback of blue-green deployments. Both strategies can be enhanced with feature flags to manage feature releases and user experiences during the transition. Canary deployment, another technique, incrementally introduces a new version to a small user group to monitor performance before full rollout, offering a different balance of risk and infrastructure use compared to blue-green and rolling strategies.