- A
Use the change feed processor library with a dedicated lease container; each worker instance claims partition leases and commits checkpoints after processing each batch
The lease container stores the last-processed continuation token per partition. On restart, a worker reads its leases and resumes from the checkpointed position. Adding more worker instances automatically redistributes leases across instances, providing linear horizontal scaling.
- B
Poll the Cosmos DB container every 30 seconds using a _ts timestamp filter to find recently modified documents
Why wrong: Timestamp polling has two problems: clock skew can cause missed documents near the query boundary, and repeated full-container scans increase RU consumption. The change feed is a purpose-built, push-based stream that avoids both issues.
- C
Subscribe to Azure Event Grid Cosmos DB events and process them in an Azure Function
Why wrong: Azure Event Grid does not natively emit per-document Cosmos DB change events at the document level in a way that supports the exactly-once-with-checkpoint semantics required. The change feed processor is the supported pattern for this use case.
- D
Enable Cosmos DB analytical store and run batch queries from an Azure Synapse Spark pool every hour
Why wrong: The analytical store serves OLAP workloads with high latency (minutes to hours). The inventory service needs near-real-time processing after each order write. Spark batch queries are unsuitable for event-driven, low-latency inventory updates.
AZ-204 Practice Question: Cosmos DB change feed processor for scalable…
This AZ-204 practice question tests your understanding of develop for azure storage. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: cosmos DB change feed. 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.
An e-commerce platform writes orders to a Cosmos DB container. A downstream inventory service must process every new or updated order exactly once, even if the inventory service restarts mid-batch. The solution must scale horizontally when order volume increases. What is the recommended design?
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
Use the change feed processor library with a dedicated lease container; each worker instance claims partition leases and commits checkpoints after processing each batch
The change feed processor library with a dedicated lease container is the recommended design because it provides exactly-once processing semantics through checkpointing, automatic partition lease management for horizontal scaling, and resilience to worker restarts by resuming from the last committed checkpoint. This pattern is purpose-built for Cosmos DB change feed consumption in distributed systems.
Key principle: Cosmos DB change feed
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use the change feed processor library with a dedicated lease container; each worker instance claims partition leases and commits checkpoints after processing each batch
Why this is correct
The lease container stores the last-processed continuation token per partition. On restart, a worker reads its leases and resumes from the checkpointed position. Adding more worker instances automatically redistributes leases across instances, providing linear horizontal scaling.
Related concept
Cosmos DB change feed
- ✗
Poll the Cosmos DB container every 30 seconds using a _ts timestamp filter to find recently modified documents
Why it's wrong here
Timestamp polling has two problems: clock skew can cause missed documents near the query boundary, and repeated full-container scans increase RU consumption. The change feed is a purpose-built, push-based stream that avoids both issues.
- ✗
Subscribe to Azure Event Grid Cosmos DB events and process them in an Azure Function
Why it's wrong here
Azure Event Grid does not natively emit per-document Cosmos DB change events at the document level in a way that supports the exactly-once-with-checkpoint semantics required. The change feed processor is the supported pattern for this use case.
- ✗
Enable Cosmos DB analytical store and run batch queries from an Azure Synapse Spark pool every hour
Why it's wrong here
The analytical store serves OLAP workloads with high latency (minutes to hours). The inventory service needs near-real-time processing after each order write. Spark batch queries are unsuitable for event-driven, low-latency inventory updates.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose Event Grid (Option C) because it is event-driven and seems simpler, but they overlook that Event Grid does not provide exactly-once processing or checkpoint-based restart resilience for Cosmos DB change feed scenarios.
Detailed technical explanation
How to think about this question
The change feed processor library works by having each worker instance acquire leases on partitions stored in a separate lease container; after processing a batch, the worker commits a checkpoint (the continuation token) to the lease container. If a worker restarts, it reads the last checkpoint and resumes from that point, ensuring no duplicates. The library also automatically redistributes leases when workers are added or removed, enabling seamless horizontal scaling.
KKey Concepts to Remember
- Cosmos DB change feed
- change feed processor
- lease container
- at-least-once delivery
- horizontal scaling
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
Cosmos DB change feed
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Review cosmos DB change feed, then practise related AZ-204 questions on the same topic to reinforce the concept.
- →
Develop for Azure storage — study guide chapter
Learn the concepts, then practise the questions
- →
Develop for Azure storage practice questions
Targeted practice on this topic area only
- →
All AZ-204 questions
997 questions across all exam domains
- →
Microsoft Azure Developer Associate AZ-204 study guide
Full concept coverage aligned to exam objectives
- →
AZ-204 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related AZ-204 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Develop Azure compute solutions practice questions
Practise AZ-204 questions linked to Develop Azure compute solutions.
Develop for Azure storage practice questions
Practise AZ-204 questions linked to Develop for Azure storage.
Implement Azure security practice questions
Practise AZ-204 questions linked to Implement Azure security.
Connect to and consume Azure services and third-party services practice questions
Practise AZ-204 questions linked to Connect to and consume Azure services and third-party services.
Monitor, troubleshoot, and optimize Azure solutions practice questions
Practise AZ-204 questions linked to Monitor, troubleshoot, and optimize Azure solutions.
AZ-204 fundamentals practice questions
Practise AZ-204 questions linked to AZ-204 fundamentals.
AZ-204 scenario practice questions
Practise AZ-204 questions linked to AZ-204 scenario.
AZ-204 troubleshooting practice questions
Practise AZ-204 questions linked to AZ-204 troubleshooting.
Practice this exam
Start a free AZ-204 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this AZ-204 question test?
Develop for Azure storage — This question tests Develop for Azure storage — Cosmos DB change feed.
What is the correct answer to this question?
The correct answer is: Use the change feed processor library with a dedicated lease container; each worker instance claims partition leases and commits checkpoints after processing each batch — The change feed processor library with a dedicated lease container is the recommended design because it provides exactly-once processing semantics through checkpointing, automatic partition lease management for horizontal scaling, and resilience to worker restarts by resuming from the last committed checkpoint. This pattern is purpose-built for Cosmos DB change feed consumption in distributed systems.
What should I do if I get this AZ-204 question wrong?
Review cosmos DB change feed, then practise related AZ-204 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Cosmos DB change feed
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More AZ-204 practice questions
- An app must store relational state and perform transactions across multiple tables with T-SQL support. Which Azure data…
- You are monitoring an Azure App Service using Application Insights. You notice that the server response time is high for…
- Which TWO services can be used to implement a publish-subscribe messaging pattern in Azure?
- You need to monitor the CPU utilization of an Azure VM in real-time and set up an alert when it exceeds 90%. Which Azure…
- You are monitoring an Azure web application with Application Insights. You notice a sudden increase in the number of fai…
- You are monitoring an Azure web app using Application Insights. You need to create a query that returns the average dura…
Last reviewed: Jun 11, 2026
This AZ-204 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 AZ-204 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.