For guidance see the article Choose a solution for integrating on-premises Active Directory with Azure.

For each option, a more detailed reference architecture is available.

Deploy AD Domain Services (AD DS) servers to Azure. Create a domain in Azure and join it to your on-premises AD forest.

See the reference architecture

Deploy AD Domain Services (AD DS) servers to Azure, but create a separate Active Directory [forest][ad-forest-defn] that is separate from the on-premises forest. This forest is trusted by domains in your on-premises forest.

See the reference architecture

Replicate an Active Directory Federation Services (AD FS) deployment to Azure, to perform federated authentication and authorization for components running in Azure.

See the reference architecture

Use Azure Active Directory (Azure AD) to create a domain in Azure and link it to an on-premises AD domain.

See the reference architecture