Describe considerations for working with non-relational data on Azure →hardMultiple SelectObjective-mapped
DP-900 Practice Question: Describe considerations for working with non-relational data on Azure
Which THREE factors should you consider when choosing between Azure Blob Storage and Azure Cosmos DB for a new application? (Choose three.)
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
✓
Global distribution and multi-region writes
(Global distribution and multi-region writes) is correct because Azure Cosmos DB supports global distribution with multi-region writes, while Azure Blob Storage does not offer multi-region writes. Option B (Data structure) is correct because Blob Storage is designed for unstructured data (blobs), whereas Cosmos DB handles semi-structured data (JSON documents) with flexible schema. Option E (Query capabilities) is correct because Cosmos DB supports complex queries (e.g., SQL, MongoDB API), while Blob Storage primarily offers key-value access by blob name. Option C (Encryption at rest) is incorrect because both services support encryption at rest. Option D (Scalability limits) is incorrect because both services are highly scalable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Global distribution and multi-region writes
Why this is correct
Azure Cosmos DB is a globally distributed database service with turnkey multi-region replication and support for multi-region writes, ensuring low-latency writes and reads anywhere in the world. Azure Blob Storage is a single-region storage service that offers only asynchronous geo-redundant replication (GRS) and does not support active writes from multiple regions. This directly affects disaster recovery, availability, and user-perceived latency for globally distributed applications.
- ✓
Data structure (unstructured vs. semi-structured)
Why this is correct
Blob Storage is designed for unstructured data such as virtual machine disks, media files, and application backups, storing each item as an opaque binary blob with no schema or internal structure to query. Cosmos DB stores semi-structured JSON documents with flexible schemas, making it suitable for data with variable attributes and nested objects. Choosing between them depends on whether your data is a simple byte stream requiring only file-level access or structured content that needs document-level manipulation and relationships.
- ✗
Encryption at rest support
Why it's wrong here
Both Azure Blob Storage and Azure Cosmos DB encrypt data at rest by default, using Azure-managed keys with the option for customer-managed keys in both services. This equivalence means encryption at rest does not favor one service over the other and therefore is not a valid consideration when selecting between them. Security teams can satisfy compliance requirements equally with either option, so other factors like availability or querying must drive the decision.
- ✗
Scalability limits
Why it's wrong here
Azure Blob Storage can scale to exabytes by distributing blobs across storage partitions and storage accounts, while Azure Cosmos DB elastically partitions data across physical partitions and can scale throughput (request units per second) and storage independently and almost infinitely. Both services are designed to meet massive cloud-scale demands, so scalability limits rarely pose a distinction in practice. The decision should instead focus on the data shape and how it will be accessed.
- ✓
Query capabilities (simple key-value vs. complex queries)
Why this is correct
Blob Storage provides only REST-based key-value access to blobs and limited metadata filtering; it cannot query the content or structure of a blob itself. Cosmos DB offers a SQL-like query language, automatic indexing, and support for stored procedures, triggers, and user-defined functions over JSON documents, enabling complex ad-hoc queries and server-side logic. If your application requires rich queries, aggregations, or transactional consistency, Cosmos DB is clearly superior to Blob Storage.
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
Go deeper
Related to this question
Learn chapter
Data Roles and Core Concepts
Key term
Semi-structured data
Semi-structured data is information that has some organizational tags or markers but does not fit into a strict table format like a spreadsheet row and column.
Key term
Encryption at rest
Encryption at rest is the practice of securing stored data by converting it into an unreadable format using cryptographic algorithms, so that even if physical or digital access to the storage medium is obtained, the data remains confidential.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DP-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DP-900 exam.