Many large customers with hundreds of thousands of users, groups, and group memberships found that synchronization from Azure Active Directory (Azure AD) to Azure Active Directory Domain Services (Azure AD DS) was taking too long. Often, it was stuck for weeks.
We’ve improved the sync performance in multiple stages. For large benchmark customers, we’ve been able to bring initial sync down to a few days.
Further, the virtual machine SKU on which Azure AD DS is hosted scales automatically based on the number of objects in the directory. This enables larger customers to get better sync performance—for both initial and ongoing sync from Azure AD.