AZ-204 Develop for Azure storage Practice Question
You are designing a solution that needs to react to changes in an Azure Cosmos DB container in real-time. Whenever a new document is inserted or updated, a downstream service must be triggered to process the change. You want to build a serverless solution that reliably captures each change exactly once. Which Azure Cosmos DB feature should you use?
⚠ Common exam trap
Candidates often confuse Change feed with triggers, but triggers are synchronous and transactional, whereas Change feed provides an asynchronous, at-least-once (with idempotent handling) stream designed for event-driven architectures.
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
✓
Change feed
The Change feed in Azure Cosmos DB is designed to capture document-level changes (inserts and updates) in the order they occur and provides an event-driven, serverless mechanism to reliably process each change exactly once. It integrates natively with Azure Functions, enabling real-time reactions without polling or custom tracking.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Stored procedures
Why it's wrong here
Azure Cosmos DB stored procedures are server-side JavaScript functions executed transactionally within a single partition key scope. While they allow complex logic and data manipulation, their primary purpose is to encapsulate database operations and ensure atomicity. They operate synchronously as part of a database transaction and lack the inherent capability to directly invoke external services or publish events for real-time, decoupled reactions to changes across the entire container.
- ✗
T-SQL queries
Why it's wrong here
T-SQL queries, or more accurately, SQL API queries in Azure Cosmos DB, are declarative statements used to retrieve, filter, and project data from containers. These queries are pull-based operations, meaning they execute upon request to fetch the current state of data. They do not offer any mechanism for real-time, push-based notifications or event streams that would allow an external solution to automatically react to data modifications as they occur within the database.
- ✓
Change feed
Why this is correct
The Azure Cosmos DB change feed provides a persistent, ordered, and sequential log of all item modifications within a container, including inserts, updates, and deletes. It acts as a durable event source, allowing external consumers, such as Azure Functions, to reliably read and process these changes in near real-time without impacting database performance. This push-based mechanism is ideal for building event-driven architectures that react to data changes for scenarios like data synchronization, materialized views, or triggering downstream processes.
- ✗
Triggers
Why it's wrong here
Azure Cosmos DB triggers are server-side JavaScript functions that execute either before (pre-trigger) or after (post-trigger) a database operation on a single item. They run synchronously within the same transaction as the item modification, primarily for data validation or transformation. However, triggers are not designed for initiating external workflows or reacting to changes across an entire container, nor can they directly invoke external services in a decoupled, asynchronous manner suitable for event-driven solutions.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
Go deeper
Related to this question
Learn chapter
Azure Functions Development
Key term
Azure Functions Bindings
Azure Functions Bindings are declarative connections that link your serverless function code to Azure services or external resources, handling input and output data automatically without writing extra networking or authentication code.
Key term
Durable Functions
Durable Functions is an extension of Azure Functions that lets you write stateful workflows in code, managing complex sequences of tasks, retries, and delays automatically.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.