The answer is Azure Cosmos DB. This service is the correct choice because it is a globally distributed, multi-model database that guarantees single-digit millisecond read latency at the 99th percentile, no matter how many Azure regions you replicate to or which consistency level you choose. On the Microsoft Azure Fundamentals AZ-900 exam, this question tests your understanding of Azure’s purpose-built database offerings, often appearing alongside traps like Azure SQL Database or Azure Table Storage—both of which lack true turnkey global distribution and multi-model support. A common memory tip is to associate “Cosmos” with “cosmic scale” and “multi-model” flexibility, and to remember that if the scenario mentions global distribution, low latency, and support for document, key-value, graph, or column-family data, the answer is always Cosmos DB.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which Azure service provides a globally distributed, multi-model database service with single-digit millisecond read latency?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Cosmos DB
Azure Cosmos DB is a globally distributed, multi-model database service that guarantees single-digit millisecond read latency at the 99th percentile, regardless of the region or consistency level. It supports multiple data models (document, key-value, graph, column-family) and provides turnkey global distribution across any number of Azure regions.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 relational database with good performance but not globally distributed by default with the same latency guarantees.
✗
Azure Database for MySQL
Why it's wrong here
Azure Database for MySQL is a managed MySQL service, not a globally distributed multi-model NoSQL database.
✓
Azure Cosmos DB
Why this is correct
Cosmos DB is globally distributed, multi-model, with single-digit millisecond latency and 99.999% availability SLA.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Cache for Redis
Why it's wrong here
Redis Cache is an in-memory cache, not a primary database solution.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure Cache for Redis (a low-latency cache) with a globally distributed multi-model database, but Redis is not a multi-model database and does not provide turnkey global distribution with multiple consistency models like Cosmos DB does.
Detailed technical explanation
How to think about this question
Azure Cosmos DB achieves its low latency through a combination of automatic indexing of all data, a write-optimized log-structured storage engine, and the use of a multi-homing API that routes requests to the nearest regional endpoint. It offers five well-defined consistency levels (strong, bounded staleness, session, consistent prefix, eventual) that allow developers to trade off between consistency, availability, and latency. In a real-world scenario, a global e-commerce platform uses Cosmos DB to serve product catalogs and user profiles with sub-10ms reads from any region, while handling millions of writes per second during flash sales.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-900 question in full detail.
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Cosmos DB — Azure Cosmos DB is a globally distributed, multi-model database service that guarantees single-digit millisecond read latency at the 99th percentile, regardless of the region or consistency level. It supports multiple data models (document, key-value, graph, column-family) and provides turnkey global distribution across any number of Azure regions.
What should I do if I get this AZ-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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