Product : Nutanix, XI Frame/current version, All Editions
Feature : Shadow pool, Update Management, Image Lifecycle Management
Content Owner:  Ajay Walia
Note that the publishing process will never interrupt a user who is in an active session. Frame will automatically wait to terminate an instance until the user has finished their session. As a result, publishing updates to your users is a "zero downtime" action.

Also, following good practice of disabling automatic updates, you can arrange to install updates during downtime and test them in the Sandbox first to ensure there are no compatibility issues before pushing out to your production workload.