You have a web application deployed as a managed instance group.

Perform a rolling-action start-update with maxSurge set to 0 and maxUnavailable set to 1.

Perform a rolling-action start-update with maxSurge set to 1 and maxUnavailable set to 0.

Create a new managed instance group with an updated instance template. Add the group to the backend service for the load balancer. When all instances in the new managed instance group are healthy, delete the old managed instance group.

Create a new instance template with the new application version. Update the existing managed instance group with the new instance template. Delete the instances in the managed instance group to allow the managed instance group to recreate the instance using the new instance template.