What deployment approach updates instances incrementally to avoid taking down the entire system at once?

• A. Rolling update
• B. Blue-green
• C. Canaries
• D. Immutable infrastructure

Answer: (A)

Rolling updates spread the deployment across the fleet, updating a subset of instances at a time while the rest continue serving traffic. This gradual approach minimizes downtime and gives you quick feedback: if problems appear, you can pause or roll back the next batch without impacting the whole system. As each batch passes health checks, the rollout proceeds until all instances are updated.

Blue-green deploys create a parallel, fully functional environment and switch traffic at once, which avoids risk during deployment but requires a complete cutover. Canaries release to a small subset first to monitor behavior before broader rollout, which is similar in spirit but targets a tiny group rather than steadily advancing across the entire fleet. Immutable infrastructure avoids in-place changes by replacing resources with new versions, so updates aren’t incremental at all.