What is the purpose of an Azure SQL Database managed instance?

The purpose of an Azure SQL Database managed instance is to provide a fully-managed SQL Server instance experience within the Azure cloud environment. This offering allows organizations to migrate their SQL Server workloads to Azure with minimal changes to their applications. It combines the benefits of SQL Server's rich features, such as database compatibility and native SQL Server capabilities, with the advantages of cloud computing, including automatic backups, scaling, high availability, and built-in security.

By utilizing a managed instance, organizations can run existing SQL Server applications in the cloud while benefiting from managed services. This includes automatic patching, updates, and much more, which significantly reduces the administrative burden on IT staff. The managed instance thus represents a bridge that allows users to leverage the cloud's capabilities without losing the familiarity and functionalities of SQL Server.

In contrast, other options focus on features that don't fully capture the essence of what an Azure SQL Database managed instance is designed to deliver. While simplified billing, multi-tenancy, and mobile application integration are important, they do not encompass the core value proposition of offering a fully-managed enterprise-grade database service aligned closely with traditional SQL Server environments.