The answer is Azure Cosmos DB API for MongoDB and MongoDB Atlas on Azure. Azure Cosmos DB API for MongoDB is correct because it layers a MongoDB-compatible API over Cosmos DB’s globally distributed, multi-model engine, allowing you to use standard MongoDB drivers while gaining turnkey global distribution, multi-region writes, and a 99.999% availability SLA. MongoDB Atlas on Azure, meanwhile, is the fully managed MongoDB service running natively in Azure data centers, offering native MongoDB features with global cluster support. On the AZ-305 exam, this question tests your ability to distinguish between Azure-native and partner services for NoSQL workloads requiring global scale; a common trap is selecting Azure SQL Database or Azure Database for MySQL, which are relational and lack MongoDB compatibility. Remember the mnemonic “Cosmos speaks Mongo, Atlas runs Mongo” to recall that Cosmos DB emulates the API while Atlas runs the actual database engine.
AZ-305 Design data storage solutions Practice Question
This AZ-305 practice question tests your understanding of design data storage solutions. 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 TWO Azure services can be used to host a MongoDB-compatible database with global distribution? (Select two.)
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 API for MongoDB
Azure Cosmos DB API for MongoDB is correct because it provides a MongoDB-compatible API layer over Cosmos DB's globally distributed, multi-model database engine. This allows you to use standard MongoDB drivers and tools while benefiting from Cosmos DB's turnkey global distribution, multi-region writes, and 99.999% availability SLA.
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 relational and does not support MongoDB wire protocol.
✓
Azure Cosmos DB API for MongoDB
Why this is correct
Cosmos DB API for MongoDB provides MongoDB compatibility with global distribution.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Database for PostgreSQL
Why it's wrong here
PostgreSQL is relational and not MongoDB-compatible.
✓
Azure Database for MongoDB (MongoDB Atlas on Azure)
Why this is correct
MongoDB Atlas is a fully managed MongoDB service on Azure.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Cache for Redis
Why it's wrong here
Redis is a key-value store, not MongoDB-compatible.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may assume only one service can host a MongoDB-compatible database, overlooking that both a native MongoDB service (Atlas) and a protocol-compatible alternative (Cosmos DB API for MongoDB) are valid, and that Azure SQL Database or PostgreSQL are relational databases that cannot serve MongoDB workloads.
Detailed technical explanation
How to think about this question
Azure Cosmos DB API for MongoDB implements the MongoDB wire protocol (version 3.2, 3.6, 4.0, and 4.2) on top of Cosmos DB's distributed storage engine, which uses a partition-key-based sharding mechanism and multi-master replication. MongoDB Atlas on Azure is a fully managed MongoDB service running on Azure infrastructure, providing native MongoDB features like replica sets and sharded clusters, but it relies on MongoDB's own global cluster management rather than Cosmos DB's underlying architecture.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-305 question in full detail.
Design data storage solutions — This question tests Design data storage solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Cosmos DB API for MongoDB — Azure Cosmos DB API for MongoDB is correct because it provides a MongoDB-compatible API layer over Cosmos DB's globally distributed, multi-model database engine. This allows you to use standard MongoDB drivers and tools while benefiting from Cosmos DB's turnkey global distribution, multi-region writes, and 99.999% availability SLA.
What should I do if I get this AZ-305 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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