Why Event Grid for event routing in Azure? - Purpose & Use Cases

The Big Idea

What if your apps could talk to each other instantly without you writing endless connection code?

The Scenario

Imagine you have many different apps and services that need to talk to each other whenever something important happens, like a new file uploaded or a user signed up.

Without a smart system, you have to write custom code for each app to check and send messages to others manually.

The Problem

This manual way is slow and confusing because every app needs to know about all others.

It's easy to make mistakes, miss messages, or create delays.

As the number of apps grows, managing all these connections becomes a big headache.

The Solution

Event Grid acts like a smart mail sorter for your apps.

It listens for events and automatically sends them only to the apps that care about them.

This way, apps don't need to know about each other directly, making communication fast, reliable, and easy to manage.

Before vs After

✗ Before

if new_file_uploaded:
    notify_app1()
    notify_app2()
    notify_app3()

✓ After

event_grid.subscribe('new_file_uploaded', app1)
event_grid.subscribe('new_file_uploaded', app2)
event_grid.publish('new_file_uploaded', file_info)
event_grid.subscribe('new_file_uploaded', app3)

What It Enables

It enables seamless, automatic, and scalable communication between many apps without complex wiring.

Real Life Example

When a customer places an order online, Event Grid can instantly notify the inventory system, shipping service, and billing app all at once, without any extra coding for each connection.

Key Takeaways

Manual event handling is slow and error-prone.

Event Grid routes events automatically to interested apps.

This simplifies communication and scales easily as you add more services.

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