AZ-204 Practice Question: Connect to and consume Azure services and third-party services
Which TWO Azure services can be used to trigger an Azure Function in response to a new blob being added to an Azure Storage account? (Choose two.)
⚠ Common exam trap
Candidates often confuse the Blob Storage trigger (which directly monitors blob containers) with Event Grid subscriptions (which require explicit configuration), or mistakenly think an HTTP trigger can be used by having a client poll for new blobs, but the question specifically asks for services that trigger the function in response to a new blob being added.
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 Blob Storage trigger
The Azure Blob Storage trigger is specifically designed to execute a function whenever a new or updated blob is detected in a storage container. It uses a polling mechanism to monitor the container and invokes the function with the blob's content and metadata as input. Option E is correct because an Azure Event Grid subscription can be configured to listen for the 'Microsoft.Storage.BlobCreated' event and route it to an Azure Function as an event-driven trigger, providing near-real-time, push-based notification without polling.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HTTP trigger
Why it's wrong here
An HTTP trigger makes an Azure Function accessible via a direct HTTP request, acting as an endpoint for external clients. While it can receive data, it does not automatically trigger based on an event originating from Azure Storage, such as a blob creation. Instead, it requires an explicit invocation from an external source, making it a pull mechanism rather than an event-driven push from the storage account.
- ✗
Queue trigger
Why it's wrong here
An Azure Queue Storage trigger activates an Azure Function when a new message is added to a specified queue. Although queues are frequently used in conjunction with blob storage (e.g., a blob upload might place a message in a queue for processing), the function itself is not directly monitoring blob events. Its execution is solely dependent on messages appearing in the configured queue, which is a distinct event source from blob changes.
- ✗
Timer trigger
Why it's wrong here
A Timer trigger executes an Azure Function on a predefined schedule using a CRON expression, making it suitable for recurring tasks at specific intervals. This trigger is designed for time-based execution, such as daily reports or data cleanup, and does not react to external events like the creation or modification of a blob in storage. Therefore, it cannot be used to automatically process new blobs as they arrive.
- ✓
Azure Blob Storage trigger
Why this is correct
The Azure Blob Storage trigger is a native binding in Azure Functions that automatically executes a function whenever a new or updated blob is detected in a specified container within an Azure Storage account. This built-in integration directly monitors the storage account for changes, providing a straightforward and efficient way to process blob events without requiring intermediary services. The function receives the blob content or metadata as input, enabling immediate processing upon creation or modification.
- ✓
Azure Event Grid subscription
Why this is correct
Azure Event Grid is a highly scalable, fully managed event routing service that can deliver events from various Azure sources, including Blob Storage, to different handlers. By creating an Event Grid subscription for a storage account and configuring an Azure Function as its endpoint, the function can be reliably triggered when specific blob events (like `Microsoft.Storage.BlobCreated`) occur. This approach decouples the event source from the handler, offers advanced filtering capabilities, and provides robust event delivery guarantees.
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 |
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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.