Question 354 of 881
Services That Can Trigger Azure Functions on Blob Upload
Which THREE Azure services can be used to trigger an Azure Function when a new blob is uploaded to a storage account?
Quick Answer
The answer is Azure Event Grid, the Blob Storage trigger (which is built on Event Grid), and Azure Event Hubs. These three services can trigger an Azure Function when a new blob is uploaded because they are designed to react to storage events or stream data in real time: Event Grid natively publishes blob creation events as a managed service, the Blob Storage trigger uses Event Grid under the hood to listen for new blobs, and Event Hubs can ingest blob upload notifications forwarded from Event Grid or via its own capture feature. On the AZ-204 exam, this tests your understanding of event-driven architecture and the distinction between event sources versus messaging brokers. A common trap is selecting Service Bus, which is a message queue not designed for blob events, or Logic Apps, which is an orchestrator that can call functions but is not a standalone trigger service. Remember the mnemonic “BEE” for Blob trigger, Event Grid, and Event Hubs to avoid picking the wrong service.
⚠ Common exam trap
Watch out — candidates often confuse Azure Logic Apps (a workflow orchestrator) with an Azure Function trigger, or mistakenly think a Service Bus queue can directly react to blob uploads without an intermediary event source.
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 (Event Grid based)
The Azure Blob Storage trigger (Event Grid based) is the native and recommended way to execute an Azure Function in response to a new blob being uploaded. It leverages Azure Event Grid to reliably deliver blob created events, enabling near-real-time, serverless processing without polling or custom code.
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 Service Bus queue
Why it's wrong here
Service Bus queues do not emit blob storage events.
- ✗
Azure Logic Apps
Why it's wrong here
Logic Apps can be triggered by blobs but is not a trigger source for Azure Functions.
- ✓
Azure Blob Storage trigger (Event Grid based)
Why this is correct
The Blob Storage trigger uses Event Grid to notify the function.
- ✓
Azure Event Hubs
Why this is correct
Event Hubs can capture blob events and forward to functions via capture or streaming.
- ✓
Azure Event Grid
Why this is correct
Event Grid can directly trigger a function via subscriptions.
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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Same concept, more angles
1 more way this is tested on AZ-204
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. 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.)
easy- A.HTTP trigger
- B.Queue trigger
- C.Timer trigger
- ✓ D.Azure Blob Storage trigger
- ✓ E.Azure Event Grid subscription
Why D: 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.
Last reviewed: Jul 4, 2026
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