AZ-900 Describe Azure architecture and services Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Azure SQL Database

  Why it's wrong here

  Azure SQL Database is also a PaaS service, but it is designed as a single managed database (or elastic pool) with a more restrictive scope that omits several on-premises SQL Server capabilities. Unlike Managed Instance, it does not offer SQL Agent, and cross-database queries are unavailable unless you use elastic query features, which add complexity. Additionally, CLR support is limited and the service imposes different configuration boundaries, so migrating a complex SQL Server workload would require application changes or workarounds—not the seamless fit that Managed Instance provides.

• ✓

  Azure SQL Managed Instance

  Why this is correct

  Azure SQL Managed Instance is a fully managed PaaS offering that runs the SQL Server database engine in Azure, delivering near-100% compatibility with on-premises SQL Server. It supports critical features like SQL Agent for job scheduling, Common Language Runtime (CLR) integration, linked servers, and cross-database queries, which are often required for enterprise lift-and-shift scenarios. Because it runs in the customer's virtual network and preserves the familiar SQL Server surface area, it allows existing applications to be migrated without rewriting code or redesigning data structures.

• ✗

  Azure Database for PostgreSQL

  Why it's wrong here

  Azure Database for PostgreSQL is a relational database service, but it uses a different SQL dialect and engine than SQL Server, so migrating an existing SQL Server database would require significant application code changes to handle incompatible T-SQL syntax, stored procedures, and data types. It is tempting because it offers a managed, scalable PostgreSQL environment for open-source workloads, and would be the correct choice if the company were migrating a PostgreSQL database or building a new application designed for PostgreSQL from the start.

• ✗

  Azure Cosmos DB

  Why it's wrong here

  Azure Cosmos DB is a globally distributed, multi-model NoSQL database service, not a relational database, so it does not accept T-SQL, stored procedures, or the schema models used by SQL Server. Even though Cosmos DB supports a SQL API, that dialect is its own query language tuned for JSON documents, and it cannot execute SQL Server-specific features like joins across relational tables or T-SQL syntax. Attempting to migrate a SQL Server database here would force a complete schema redesign, a full data-model rewrite, and substantial application code changes, making it fundamentally unsuitable for a lift-and-shift of an existing SQL Server workload.

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