How do blue-green and rolling deployments differ in terms of risk and rollback speed?

A rolling deployment replaces instances incrementally (e.g., one at a time), which uses less extra capacity but means a bad release is live for some users during the rollout and rollback means re-rolling the old version back incrementally. Blue-green deployment runs the new version fully alongside the old version and switches traffic atomically once the new version is verified healthy, making rollback nearly instantaneous (switch traffic back) at the cost of requiring double the infrastructure capacity during the transition. Teams often choose rolling for cost efficiency and blue-green when ro