AZ-204 Develop for Azure storage Practice Question
You are developing an Azure Function that processes images uploaded to a storage account. The function must generate thumbnails and write them to a separate container. You need to configure the function to trigger when a new blob is created, and you want to use the latest SDK with minimal code. Which trigger binding should you use?
⚠ Common exam trap
The trap here is assuming BlobTrigger is always the simplest and most direct way to react to blob uploads, when in fact it uses polling and may introduce delays.
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
✓
EventGridTrigger with an event subscription to the storage account's BlobCreated event.
The EventGridTrigger leverages Azure Event Grid to deliver blob creation events to the function in near real-time, eliminating polling and reducing code. It is the recommended trigger for reactive blob processing with the latest SDKs. BlobTrigger, QueueTrigger, and HttpTrigger either rely on polling, require additional components, or are not event-driven for storage, making them less efficient or more complex for this scenario.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HttpTrigger with a webhook registered to the storage account.
Why it's wrong here
HttpTrigger exposes an endpoint that can be called by external systems, but Azure Storage does not natively send webhooks for blob creation events. You would need to build a custom mechanism to detect blob uploads and then call the HTTP endpoint. This introduces unnecessary complexity and latency. EventGridTrigger is designed specifically to handle storage events without custom plumbing. HttpTrigger is suitable for APIs, not for reacting to storage events.
- ✓
EventGridTrigger with an event subscription to the storage account's BlobCreated event.
Why this is correct
EventGridTrigger is the recommended approach for reacting to blob creation events in Azure Storage. It provides near real-time processing by leveraging Azure Event Grid, which pushes events to the function. This eliminates the need for polling and reduces latency. The latest Azure Functions SDKs have first-class support for Event Grid triggers, and you can easily filter events to only BlobCreated. This approach is more scalable and efficient for image processing workloads, making it the best fit for the scenario.
- ✗
BlobTrigger with the path parameter set to the source container.
Why it's wrong here
BlobTrigger is designed for scenarios where you need to react to blob creation and update events in a storage account. However, it relies on Azure Storage polling and logs, which can introduce latency and is not the most efficient for high-scale scenarios. For minimal code and latest SDK integration, EventGridTrigger is preferred because it provides near real-time event-driven processing. BlobTrigger may still be valid for simple scenarios, but it is not the optimal choice when you want to leverage event-based triggers with the latest SDK.
- ✗
QueueTrigger with a message added to a queue when a blob is uploaded.
Why it's wrong here
QueueTrigger requires an external process to add a message to a queue when a blob is uploaded. This adds complexity because you need to implement additional logic to monitor blob creation and enqueue messages. While it decouples the trigger from the storage account, it is not the simplest solution and does not directly respond to blob events. For minimal code and direct integration with blob creation, EventGridTrigger is superior. QueueTrigger is better suited for scenarios where you already have a queue-based workflow.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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