Check out the maximum limits of Active Directory
Did you know that there are certain pre-defined limits of Active Directory? For example, there is a maximum on the number of objects (users, groups, computers, organizational units, group policies, etc.) that can exist in Active Directory; specifically, not more than 2.15 billion objects can exist in the directory and only about 1 billion security principles (users, groups, and computers) can exist. To learn more about specific limitations of Active Directory, check out the article
Active Directory Maximum Limits.
