AZ-204 Develop Azure compute solutions Practice Question
You are developing a web app that processes images uploaded by users. The processing can take up to 30 seconds per image. You need to ensure that the web app remains responsive and can handle spikes in traffic. Which Azure service should you use to offload the image processing?
⚠ Common exam trap
Test-takers frequently confuse Azure Event Grid's event-driven architecture with a queueing mechanism, overlooking that Event Grid does not provide message persistence or retry for long-running processing, whereas Queue Storage is explicitly designed for asynchronous work offloading.
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
✓
Azure Queue Storage
Azure Queue Storage is correct because it provides a durable, asynchronous message queue that can decouple the web app's frontend from the long-running image processing task. By placing a message for each image onto a queue, the web app can immediately return a response to the user, while a background worker (e.g., an Azure Function or WebJob) polls the queue and processes images as capacity allows. This pattern ensures the web app remains responsive under traffic spikes, as the queue acts as a buffer that scales independently.
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 Cosmos DB
Why it's wrong here
Azure Cosmos DB is a globally distributed, multi-model database service primarily designed for storing and querying data with low latency and high availability. While it can store documents, it is fundamentally a persistent data store, not a transient message broker or queue service. Its purpose is data management and retrieval, making it unsuitable for the temporary storage and ordered processing of messages required for asynchronous task decoupling like image processing.
- ✓
Azure Queue Storage
Why this is correct
Azure Queue Storage provides a robust, scalable, and durable message queuing service ideal for decoupling components of an application. It enables the web app to quickly enqueue image processing requests without waiting for completion, significantly improving responsiveness and resilience. This buffering capability effectively handles spikes in demand, ensuring that backend workers can process images asynchronously at their own pace, preventing system overload and ensuring reliable task execution.
- ✗
Azure Event Grid
Why it's wrong here
Azure Event Grid is an event routing service that enables applications to react to events in real time, delivering notifications from various sources to subscribed handlers. Unlike a message queue, Event Grid is designed for reactive, push-based event delivery rather than holding messages for pull-based processing by worker applications. It excels at event-driven architectures where immediate notification and fan-out are key, not for durable, ordered task queuing for backend workers.
- ✗
Azure SignalR Service
Why it's wrong here
Azure SignalR Service facilitates real-time, bidirectional communication between servers and clients over protocols like WebSockets, primarily for interactive web applications. It is designed for scenarios requiring immediate updates to connected clients, such as chat applications or live dashboards, not for storing or processing backend tasks. Using SignalR for queuing image uploads would be entirely inappropriate, as it lacks message durability, ordering, and the producer-consumer model necessary for asynchronous task processing.
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