Which type of database is Azure Database for PostgreSQL? (DP-900)

Correct answer: A. Platform as a service (PaaS).
Azure Database for PostgreSQL is a fully managed database service provided by Microsoft as a platform as a service (PaaS) offering.
In a PaaS model, the cloud provider (in this case, Microsoft) is responsible for managing the underlying infrastructure, including the operating system, database software, and other components. This allows the customer to focus on developing and deploying their applications, without having to worry about the underlying infrastructure.

The other options are not correct:
B. Infrastructure as a service (IaaS): IaaS provides virtual machines and other infrastructure components, but the customer is responsible for managing the operating system and software installed on the VMs. Azure Database for PostgreSQL is a PaaS offering, not an IaaS service.
C. Microsoft SQL Server: Azure Database for PostgreSQL is a service that provides the PostgreSQL database engine, not Microsoft SQL Server.
D. on-premises: Azure Database for PostgreSQL is a cloud-based service, not an on-premises database solution.

Therefore, Azure Database for PostgreSQL is a platform as a service (PaaS) offering, where Microsoft manages the underlying infrastructure and the customer can focus on their application and data.