AZ-204 Develop Azure compute solutions Practice Question
You develop a serverless application using Azure Functions. The function must process images uploaded to a blob container. You need to ensure the function runs only when a new blob is created, and that it scales out automatically for high upload volumes. Which trigger and hosting plan combination should you use?
⚠ Common exam trap
The trap here is that candidates might confuse the Blob trigger with other triggers (HTTP, Queue, Timer) that can indirectly process blobs, but the question explicitly requires the function to run only when a new blob is created, which only the Blob trigger directly supports.
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
✓
Blob trigger + Consumption plan
A Blob trigger is designed to run a function when a blob is created or updated in Azure Blob Storage, which directly matches the requirement to process images only when a new blob is uploaded. The Consumption plan provides automatic scaling based on demand, handling high upload volumes by dynamically allocating resources without manual intervention. This combination ensures event-driven execution and cost-effective scaling.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Blob trigger + Consumption plan
Why this is correct
The Blob trigger is the most direct and efficient mechanism for reacting to new or updated blobs in Azure Storage. It leverages Azure Event Grid internally to provide an immediate, event-driven response without polling. When combined with the Consumption plan, the function scales automatically from zero instances to handle high volumes of uploads, ensuring cost-effectiveness by only charging for actual execution time.
- ✗
HTTP trigger + Consumption plan
Why it's wrong here
An HTTP trigger requires an external client to initiate its execution by sending an explicit HTTP request to the function's endpoint. This means it does not inherently respond to blob upload events. Implementing this for blob processing would necessitate an additional service, such as an Azure Logic App or another function, to monitor blob storage and then invoke the HTTP-triggered function, introducing unnecessary architectural complexity and potential latency.
- ✗
Queue trigger + Consumption plan
Why it's wrong here
A Queue trigger is designed to activate an Azure Function when a new message is added to an Azure Storage Queue. To use this for processing blob uploads, an intermediate step would be required, such as an Event Grid subscription pushing blob creation events to a queue. This introduces an additional component and potential latency, making it less direct and efficient than using a native Blob trigger for event-driven blob processing.
- ✗
Timer trigger + Consumption plan
Why it's wrong here
The Timer trigger executes an Azure Function on a predefined, recurring schedule, rather than in response to specific events. While it could be configured to periodically scan blob storage for new files, this polling-based approach is inherently inefficient and introduces significant latency between a blob's upload and its processing. It would also consume resources even when no new blobs are present, making it unsuitable for immediate, event-driven responses to uploads.
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
Go deeper
Related to this question
Learn chapter
Azure Functions Development
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.
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.
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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.