The answer is the Cassandra API for Azure Cosmos DB. This is correct because the Cassandra API is wire-protocol-compatible with Apache Cassandra, allowing you to use existing Cassandra Query Language (CQL) tools, drivers, and code with minimal changes while migrating to a fully managed, globally distributed NoSQL service with low-latency performance. On the Microsoft Azure Data Fundamentals DP-900 exam, this question tests your understanding of how each Cosmos DB API maps to specific source databases and workloads; a common trap is confusing the Table API (which uses a different query syntax) or the Core (SQL) API, which does not support CQL. Remember that if the scenario explicitly mentions preserving CQL or migrating from Apache Cassandra, the Cassandra API is the only choice that provides direct protocol compatibility. A helpful memory tip is to think “Cassandra API for Cassandra code”—the name tells you exactly which source database it supports.
DP-900 Practice Question: Describe considerations for working with non-relational data on Azure
This DP-900 practice question tests your understanding of describe considerations for working with non-relational data on azure. 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.
A company has an existing IoT application that uses Apache Cassandra for time-series sensor data. They want to migrate to Azure's fully managed NoSQL database service while continuing to use the Cassandra Query Language (CQL) and benefiting from global distribution and low latency. Which Azure Cosmos DB API should they use?
Why wrong: Incorrect. The Core (SQL) API uses a SQL-like query language, not Cassandra Query Language. It would require rewriting application queries and data model.
B
MongoDB API
Why wrong: Incorrect. The MongoDB API is compatible with MongoDB drivers and uses MongoDB's query language, not CQL. It is intended for MongoDB workloads.
C
Cassandra API
Correct. The Cassandra API provides compatibility with the Apache Cassandra wire protocol and CQL, enabling a seamless migration from a Cassandra cluster to a globally distributed, fully managed service.
D
Gremlin API
Why wrong: Incorrect. The Gremlin API is designed for graph data and uses the Gremlin traversal language. It is not suitable for the tabular, time-series workload that uses CQL.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Cassandra API
The Cassandra API for Azure Cosmos DB is wire-protocol-compatible with Apache Cassandra, meaning you can use existing CQL (Cassandra Query Language) tools, drivers, and code with minimal changes. It provides a fully managed, globally distributed NoSQL database with low-latency reads and writes, which directly matches the company's requirement to migrate from self-managed Cassandra while preserving their CQL-based application logic.
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.
✗
Core (SQL) API
Why it's wrong here
Incorrect. The Core (SQL) API uses a SQL-like query language, not Cassandra Query Language. It would require rewriting application queries and data model.
✗
MongoDB API
Why it's wrong here
Incorrect. The MongoDB API is compatible with MongoDB drivers and uses MongoDB's query language, not CQL. It is intended for MongoDB workloads.
✓
Cassandra API
Why this is correct
Correct. The Cassandra API provides compatibility with the Apache Cassandra wire protocol and CQL, enabling a seamless migration from a Cassandra cluster to a globally distributed, fully managed service.
Related concept
Read the scenario before looking for a memorised answer.
✗
Gremlin API
Why it's wrong here
Incorrect. The Gremlin API is designed for graph data and uses the Gremlin traversal language. It is not suitable for the tabular, time-series workload that uses CQL.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the 'Cassandra API' with the 'Core (SQL) API' because both support SQL-like syntax, but only the Cassandra API uses the native CQL wire protocol and wide-column storage model required for time-series sensor data.
Detailed technical explanation
How to think about this question
Under the hood, the Cassandra API implements the same CQL binary protocol (v4) and partition-key hashing as Apache Cassandra, allowing seamless migration of existing client drivers (e.g., DataStax Java Driver). Cosmos DB's global distribution uses multi-region writes and tunable consistency levels (e.g., Eventual, Consistent Prefix) that map directly to Cassandra's consistency levels like QUORUM or LOCAL_QUORUM, enabling low-latency reads from the nearest region. A real-world scenario: a manufacturing company migrating from a self-hosted 10-node Cassandra cluster to Cosmos DB Cassandra API can reuse their existing CQL INSERT/ SELECT statements and Spark connectors without rewriting application code.
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 DP-900 question in full detail.
Describe considerations for working with non-relational data on Azure — This question tests Describe considerations for working with non-relational data on Azure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Cassandra API — The Cassandra API for Azure Cosmos DB is wire-protocol-compatible with Apache Cassandra, meaning you can use existing CQL (Cassandra Query Language) tools, drivers, and code with minimal changes. It provides a fully managed, globally distributed NoSQL database with low-latency reads and writes, which directly matches the company's requirement to migrate from self-managed Cassandra while preserving their CQL-based application logic.
What should I do if I get this DP-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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