AZ-900 Describe Azure architecture and services Practice Question
Which Azure service provides a managed relational database compatible with PostgreSQL?
⚠ Common exam trap
A common mix-up: candidates confuse Azure Cosmos DB for PostgreSQL (a distributed, sharded database) with the standard managed Azure Database for PostgreSQL, leading candidates to select the Cosmos DB option when the question asks for a managed relational database compatible with PostgreSQL.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Database for PostgreSQL
Azure Database for PostgreSQL is a fully managed, enterprise-ready relational database service built on the open-source PostgreSQL engine. It provides built-in high availability, automated backups, and scaling, making it the correct choice for a managed PostgreSQL-compatible database in Azure.
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 a fully managed relational database service built on the proprietary Microsoft SQL Server engine. It does not support the PostgreSQL wire protocol, T-SQL syntax, or PostgreSQL-specific features like JSON/JSONB operations and extension management. This option is incorrect because it cannot run a PostgreSQL workload, and choosing it would require migrating the application to Microsoft's SQL dialect.
- ✓
Azure Database for PostgreSQL
Why this is correct
Azure Database for PostgreSQL is the fully managed, correct service for PostgreSQL workloads, providing the community edition of the PostgreSQL engine with built-in high availability, automated backups, and scalable compute and storage. It preserves full compatibility with PostgreSQL's SQL dialect, data types, indexing, and extension ecosystem, and supports both single server and flexible server deployment options. This makes it the appropriate choice for running a standard PostgreSQL database on Azure.
- ✗
Azure Cosmos DB for PostgreSQL
Why it's wrong here
Azure Cosmos DB for PostgreSQL, formerly known as Citus, is a distributed PostgreSQL service that uses the PostgreSQL engine but adds horizontal sharding by creating distributed tables across multiple nodes. It is designed for large-scale, multi-tenant applications or analytical workloads requiring massive scalability, not for a typical single-node PostgreSQL database. Thus, although it is built on PostgreSQL, it is not the standard managed offering and would be an overkill or misaligned choice for a basic PostgreSQL scenario; Azure Database for PostgreSQL is the intended service.
- ✗
Azure Database for MariaDB
Why it's wrong here
Azure Database for MariaDB is a managed service that runs the MariaDB database engine, which is a community-developed fork of MySQL. While it offers MySQL-compatible features, it does not use the PostgreSQL engine, so it cannot execute PostgreSQL's procedural language (PL/pgSQL), data types, or extensions. It is the wrong choice for a PostgreSQL workload because the application would need to be rewritten to use MariaDB/MySQL syntax and functions.
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Azure Regions and Geographies
Key term
High availability
High availability is a system design approach that aims to keep applications and services operational and accessible with minimal downtime, even when some components fail.
Key term
Availability
Availability is the measure of how often a system or service is operational and accessible when needed, typically expressed as a percentage of uptime.
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