The objective of the KB is to assist with easing performance issues when hitting the AD service. Most issues will arise when using the picker control or lookup control where the source is either ADv2, SharePoint People Picker or URM. SharePoint People Picker and URM will go to cache, but if user/group is expired will then have to hit AD. Also getUsers() will always go to AD thus this is the most applicable scenario as this is the method most likely fired when using URM as a source. The most common scenario is a form that sits on top of People/Group properties in SharePoint.
Before You Begin
Before you begin you should be familiar with using people picker and / or search controls, as well as configuring the source and configuring data passed when firing off createListItem().
When configuring the source, avoid using FQN as a filter as this does not exist in AD thus performance will be a factor.
Also, when firing createListItem() using people picker via form via SharePoint UI end user, should pass a unique value when executing method via property that is not unique. An example would be passing email address vs passing display name as display name is not unique thus performance and other issues may arise.