When applying changes to a proxy service, user traffic is slowed and CPU utilization increases for a short period of time. 

When a proxy service is modified, the appliance takes a moment to update network configuration to listen for connections that apply to the new service, (port, IP, and ranges for each). Once the update is complete, service returns to normal.

This is expected behavior. To avoid issues with performance related to proxy service object changes, Blue Coat recommends that changes are made during off-peak hours, or during a maintenance window.