AZ-900 Describe Azure architecture and services Practice Question
Which Azure database service provides ACID-compliant transactional support with row-level locking, ideal for online retail order processing?
⚠ Common exam trap
It's easy for candidates to confuse 'cloud-native' or 'globally distributed' (Cosmos DB) with 'transactional reliability,' overlooking that ACID compliance and row-level locking are exclusive to relational databases like Azure SQL Database.
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 SQL Database
Azure SQL Database is a fully managed relational database engine that provides full ACID (Atomicity, Consistency, Isolation, Durability) compliance and supports row-level locking, making it ideal for online transaction processing (OLTP) workloads such as retail order processing. It ensures data integrity and concurrency control, which are critical for handling simultaneous order transactions without conflicts.
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 Cosmos DB
Why it's wrong here
Azure Cosmos DB is a multi-model NoSQL database that guarantees ACID for single-document operations but does not offer full multi-document ACID transactions or complex SQL joins across items. Its design prioritizes horizontal scaling and low latency over expressive relational integrity, so it is not suited for transactional SQL workloads that need strong consistency across multiple related entities.
- ✓
Azure SQL Database
Why this is correct
Azure SQL Database is a fully managed relational database engine that provides complete ACID compliance, row-level locking, multi-statement transactions, and rich SQL capabilities such as joins, indexes, and constraints. It is purpose-built for OLTP workloads that require data consistency and concurrent transactional integrity, making it the correct choice here.
- ✗
Azure Table Storage
Why it's wrong here
Azure Table Storage is a schemaless NoSQL key-value store that organizes data into entities addressed by partition key and row key. It supports only simple point and range queries, not arbitrary joins, multi-item transactions, or SQL semantics. Thus it lacks the ACID guarantees and query capability required for complex OLTP transactional workloads.
- ✗
Azure Blob Storage
Why it's wrong here
Azure Blob Storage is an object storage service designed for unstructured data such as images, videos, and backups. It offers no query engine, no relational schema, and no transaction support across blobs. Because it only manages flat files or blobs, it cannot serve as a transactional database for OLTP systems.
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