What is a 'rolling restart' in a web server deployment and why is it preferred over a full restart for zero-downtime deployments?

• A.A rolling restart restarts all instances simultaneously for consistency and is the standard approach
• B.Rolling restarts are slower and should only be used when zero downtime isn't required
• C.Rolling restarts are only applicable to containerized (Docker/Kubernetes) deployments; bare metal servers must do full restarts
• D.A rolling restart takes instances out of rotation one at a time (or in small batches), restarts them with new code/config, and returns them to rotation before proceeding to the next batch. This ensures at least some instances are always serving traffic during the restart cycle, achieving zero downtime. In contrast, a full restart would cause a complete outage