Universal Containers (UC) is expecting to have nearly 5 million shipments records in its Salesforce org. Each shipment record has up to 10 child shipment item records. The Shipment custom object has an Organization-wide Default (OWD) sharing model set to Private and the Shipment Item custom object has a Master-Detail relationship to Shipment. There are 25 sharing rules set on the Shipment custom object, which allow shipment records to be shared to each of UC's 25 business areas around the globe. These sharing rules use public groups, one for each business area plus a number of groups for management and support roles. UC has a high turnover of Sales Reps and often needs to move Sales Reps between business areas in order to meet local demand. What feature would ensure that performance, when moving Sales Reps between regions, remains adequate while meeting existing requirements?