Event Grid for event routing in Azure - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Event Grid subscription filtering behavior

You have an Azure Event Grid topic with multiple event subscriptions. One subscription uses a filter to only receive events where the eventType is Contoso.Items.Created. What happens when an event with eventType Contoso.Items.Updated is published?

A The subscription does not receive the event because the event type does not match the filter.

B The event is rejected by Event Grid and not delivered to any subscription.

C The subscription receives the event but with a warning.

D The subscription receives the event because it matches the topic.

💡 Hint

Think about how filters work in Event Grid subscriptions.

Event Grid delivers events only to subscriptions whose filters match the event properties. If the event type does not match the filter, the event is not delivered to that subscription.

❓ Architecture

intermediate

Choosing Event Grid for event routing

You want to build a system where multiple services react to events from various sources in near real-time. Which feature of Azure Event Grid makes it suitable for this scenario?

A Event Grid only supports events from Azure Blob Storage.

B Event Grid provides push-based event delivery with low latency and supports multiple subscribers.

C Event Grid requires polling to receive events.

D Event Grid supports direct database queries for event storage.

💡 Hint

Consider how Event Grid delivers events to subscribers.

Event Grid uses push-based delivery to send events to multiple subscribers quickly and supports many event sources, making it ideal for near real-time event routing.

❓ security

advanced

Securing Event Grid event subscriptions

You want to ensure that only authorized services can subscribe to your Event Grid topic. Which method provides the best security for event subscription authentication?

A Use Azure Active Directory (AAD) authentication with managed identities for the subscription endpoint.

B Use a shared access key in the subscription endpoint URL.

C Use IP filtering on the Event Grid topic to allow all IPs.

D No authentication is needed because Event Grid is secure by default.

💡 Hint

Think about modern Azure security best practices.

Using Azure Active Directory authentication with managed identities ensures secure, token-based authentication for event subscriptions, which is more secure than shared keys or IP filtering alone.

❓ Configuration

advanced

Event Grid dead-letter destination configuration

You want to configure an Event Grid subscription to send undeliverable events to a dead-letter destination. Which of the following is a valid dead-letter destination for Event Grid?

A Azure SQL Database table

B Azure Virtual Machine disk

C Azure Blob Storage container

D Azure Cosmos DB container

💡 Hint

Dead-letter destinations must be storage services that can hold event data.

Event Grid supports Azure Blob Storage containers as dead-letter destinations to store undeliverable events for later inspection or replay.

✅ Best Practice

expert

Optimizing Event Grid event routing for high scale

You have an Event Grid topic receiving thousands of events per second. To optimize event routing and reduce latency, which approach is best?

A Create a single subscription with no filters to receive all events and process filtering in the subscriber.

B Use polling on the Event Grid topic to batch events before processing.

C Disable retry policies to avoid duplicate events.

D Create multiple subscriptions with filters to route only relevant events to each subscriber.

💡 Hint

Think about how filtering affects event delivery and processing load.

Using multiple subscriptions with filters reduces unnecessary event delivery and processing, improving performance and reducing latency at scale.

Practice

1. What is the main purpose of Azure Event Grid in cloud applications?

easy

A. To route events from sources to event handlers automatically

B. To store large amounts of data for analytics

C. To create virtual machines for compute power

D. To manage user identities and access control

Solution

1. Step 1: Understand Event Grid's role

   Event Grid is designed to route events from sources to handlers automatically, enabling reactive applications.

2. Step 2: Compare with other services

   Other options describe different Azure services: storage, compute, and identity management, not event routing.

3. Final Answer:

   To route events from sources to event handlers automatically -> Option A

4. Quick Check:

   Event routing = To route events from sources to event handlers automatically [OK]

Hint: Event Grid moves events, not data or users [OK]

Common Mistakes:

• Confusing Event Grid with storage services
• Thinking Event Grid manages virtual machines
• Mixing Event Grid with identity services

2. Which Azure CLI command correctly creates an Event Grid subscription named mySub for a topic myTopic?

easy

A. az eventgrid subscription create --topic myTopic --name mySub

B. az eventgrid event-subscription create --name mySub --source-resource-id myTopic

C. az eventgrid topic create --name mySub --source myTopic

D. az eventgrid event-subscription create --name mySub --source-resource-id /subscriptions/.../resourceGroups/.../providers/Microsoft.EventGrid/topics/myTopic

Solution

1. Step 1: Identify correct CLI syntax for event subscription

   The command requires the full resource ID for the source topic using --source-resource-id.

2. Step 2: Evaluate options

   az eventgrid event-subscription create --name mySub --source-resource-id /subscriptions/.../resourceGroups/.../providers/Microsoft.EventGrid/topics/myTopic uses the full resource ID format, which is required. az eventgrid event-subscription create --name mySub --source-resource-id myTopic lacks full resource ID, C creates a topic not subscription, D uses wrong command.

3. Final Answer:

   az eventgrid event-subscription create --name mySub --source-resource-id /subscriptions/.../resourceGroups/.../providers/Microsoft.EventGrid/topics/myTopic -> Option D

4. Quick Check:

   Full resource ID needed for subscription creation [OK]

Hint: Use full resource ID with --source-resource-id for subscriptions [OK]

Common Mistakes:

• Using topic creation command instead of subscription
• Omitting full resource ID in source
• Using incorrect command names

3. Given this Azure CLI command output snippet for an Event Grid subscription:

{
  "destination": {
    "endpointType": "WebHook",
    "properties": {
      "endpointUrl": "https://myapp.com/api/events"
    }
  },
  "filter": {
    "subjectBeginsWith": "orders/",
    "subjectEndsWith": ".json"
  }
}

Which events will be delivered to the webhook endpoint?

medium

A. Only events with subjects exactly 'orders/.json'

B. All events regardless of subject

C. All events with subjects starting with 'orders/' and ending with '.json'

D. Events with subjects containing 'orders/' anywhere

Solution

1. Step 1: Understand subject filters in Event Grid

   The filter uses subjectBeginsWith and subjectEndsWith to select events whose subject starts with 'orders/' and ends with '.json'.

2. Step 2: Analyze options

   All events with subjects starting with 'orders/' and ending with '.json' matches the filter exactly. Only events with subjects exactly 'orders/.json' is too strict (exact match), C ignores filters, D is incorrect because 'contains' is not used.

3. Final Answer:

   All events with subjects starting with 'orders/' and ending with '.json' -> Option C

4. Quick Check:

   Subject filters = startsWith + endsWith [OK]

Hint: Filters combine start and end patterns, not exact or contains [OK]

Common Mistakes:

• Assuming exact subject match required
• Ignoring subject filters and expecting all events
• Confusing contains with beginsWith or endsWith

4. You created an Event Grid subscription but your webhook endpoint is not receiving events. Which of these is the most likely cause?

medium

A. The Event Grid topic does not exist

B. The webhook endpoint URL is incorrect or unreachable

C. You forgot to create an Azure Storage account

D. The subscription filter matches all events

Solution

1. Step 1: Check webhook endpoint accessibility

   If the webhook URL is wrong or the endpoint is down, events cannot be delivered.

2. Step 2: Evaluate other options

   Topic existence is important but usually checked at creation; storage account is unrelated; a filter matching all events would not block delivery.

3. Final Answer:

   The webhook endpoint URL is incorrect or unreachable -> Option B

4. Quick Check:

   Endpoint must be reachable for event delivery [OK]

Hint: Check webhook URL and network access first [OK]

Common Mistakes:

• Assuming storage account is needed for Event Grid
• Ignoring endpoint network issues
• Thinking filters block all events by default

5. You want to route events from multiple Azure Blob Storage accounts to a single Azure Function using Event Grid. What is the best approach to achieve this?

hard

A. Create an Event Grid subscription for each storage account, all pointing to the same Azure Function endpoint

B. Create one Event Grid subscription on one storage account and expect it to receive events from all accounts

C. Use Azure Logic Apps to poll each storage account and forward events to the function

D. Configure the Azure Function to listen directly to all storage accounts without Event Grid

Solution

1. Step 1: Understand Event Grid subscription scope

   Event Grid subscriptions are scoped to a single resource, so each storage account needs its own subscription.

2. Step 2: Evaluate options

   Create an Event Grid subscription for each storage account, all pointing to the same Azure Function endpoint correctly creates multiple subscriptions pointing to one function. Create one Event Grid subscription on one storage account and expect it to receive events from all accounts is invalid because one subscription cannot cover multiple accounts. Use Azure Logic Apps to poll each storage account and forward events to the function adds unnecessary polling. Configure the Azure Function to listen directly to all storage accounts without Event Grid is not supported as functions rely on Event Grid for event routing.

3. Final Answer:

   Create an Event Grid subscription for each storage account, all pointing to the same Azure Function endpoint -> Option A

4. Quick Check:

   One subscription per source resource [OK]

Hint: Each source needs its own subscription to route events [OK]

Common Mistakes:

• Assuming one subscription covers multiple sources
• Using polling instead of event-driven routing
• Expecting Azure Function to listen without Event Grid