Azure Event Grid

1. What is Azure Event Grid?

• Designed for high scalability and low latency.

• Enables decoupling of event producers and consumers.

• Supports built-in events from Azure services and custom events from your own applications.

• Supports advanced event filtering and intelligent routing.

• Provides reliable delivery with retry policies and dead-letter storage.

2. Core Concepts and Components

3. Event Data and Schemas

• Supports CloudEvents 1.0 standard for compatibility.

• Custom events support arbitrary JSON payloads.

• System events have predefined schemas (e.g., BlobCreated event from Azure Storage).

• Each event contains properties like id, eventType, subject, eventTime, data, and dataVersion.

4. Event Delivery and Reliability

• Push model: Event Grid pushes events to subscribers over HTTPS or MQTT.

• Retry policies: Event Grid retries delivery for up to 24 hours with exponential backoff if the subscriber endpoint is unavailable.

• Supports dead-lettering to Azure Blob Storage or Storage Queues for failed events.

• Guarantees at-least-once delivery semantics.

5. Supported Event Sources and Handlers

Azure Event Sources include:

• Azure Blob Storage

• Azure Resource Groups

• Azure Maps

• Azure IoT Hub

• Azure Service Bus

• Custom Topics from user applications

• Third-party SaaS partners (e.g., Auth0, Microsoft Graph)

Event handlers include:

• Azure Functions

• Azure Logic Apps

• Event Hubs

• Service Bus queues or topics

• Webhooks (any HTTPS endpoint)

• Azure Automation Runbooks

6. Pricing Model

• Consumption-based Pricing:
• $0.60 per million operations after first 100,000 free operations/month.
• Operations include event ingress, advanced matching, delivery attempts, and management API calls.

• No upfront cost or fixed commitment.

• Cost-effective for both low and high volumes due to pay-per-use model.

7. Scalability

• Automatically scales to handle millions of events per second globally.

• Built-in load balancing and fault tolerance.

• Support for fan-out pattern: multiple event subscriptions can receive the same event.

• Supports both push and pull delivery methods, including MQTT for IoT scenarios.

8. Security and Identity Management (IAM)

• Integration with Azure Active Directory (Azure AD) for authentication and RBAC over Event Grid resources.

• Supports managed identities for secure authentication by event handlers.

• Data in transit secured by TLS.

• Role-based access control (RBAC) secures management and event publishing.

• Private Endpoints (Azure Private Link) for private network access to Event Grid topics and domains.

• Supports IP filtering and firewall rules.

9. Deployment and Configuration

Resource creation and management:

• Create Event Grid Topics, Domains, and Subscriptions via:
• Azure Portal
• Azure CLI
• PowerShell
• ARM templates / Bicep scripts
• SDKs (e.g., .NET, JavaScript)

CLI example to create a custom topic:

az eventgrid topic create --name myCustomTopic --resource-group myResourceGroup --location eastus

Sample creation of event subscription to Azure Function:

az eventgrid event-subscription create \
--resource-id "/subscriptions/{subId}/resourceGroups/myResourceGroup/providers/Microsoft.EventGrid/topics/myCustomTopic" \
--name mySubscription \
--endpoint https://myfunctionapp.azurewebsites.net/runtime/webhooks/eventgrid?functionName=myFunction

10. Development: Publishing and Consuming Events

Publishing custom events (C# example using Event Grid SDK):

using Azure.Messaging.EventGrid;
using System;
using System.Threading.Tasks;

var topicEndpoint = "https://<your-topic>.<region>-1.eventgrid.azure.net/api/events";
var topicKey = "<your-topic-key>";

var credential = new AzureKeyCredential(topicKey);
var client = new EventGridPublisherClient(new Uri(topicEndpoint), credential);

var events = new[]
{
    new EventGridEvent(
        subject: "NewFileUploaded",
        eventType: "FileUploaded",
        dataVersion: "1.0",
        data: new { FileName = "report.pdf", Size = 12345 }
    )
};

await client.SendEventsAsync(events);
Console.WriteLine("Event published.");

Handling events with Azure Functions:

[FunctionName("EventGridTriggerCSharp")]
public static void Run([EventGridTrigger] EventGridEvent eventGridEvent, ILogger log)
{
    log.LogInformation($"Event Type: {eventGridEvent.EventType}");
    log.LogInformation($"Data: {eventGridEvent.Data.ToString()}");
}

11. Advanced Features

• Event Domains: Multi-tenant large-scale event routing, simplifying management of many topics.

• Event Filtering: Allows routing events based on prefixes, suffixes, or advanced subject or event type filtering.

• Dead-lettering: Storage for undelivered events for audit and troubleshooting.

• Input Mapping: Supported in Event Grid Domains to transform event payloads before delivery.

• Partner Event Source: Integration with SaaS providers to deliver partner events through Event Grid.

12. Monitoring and Diagnostics

• Azure Monitor integration tracks metrics such as event ingress, successful/failed deliveries, latency, and throttling.

• Diagnostic logs can be enabled for operations and event delivery.

• Alerts can be configured to notify based on failures or delays.

• Use the Azure Portal to view event subscription health and dead-letter queues.

13. Summary Table for Azure Event Grid

FAQ

• Event Sources: Azure services or custom applications that produce events (e.g., Blob Storage, IoT Hub).

• Topics: Endpoints where events are published; can be system topics (for Azure services) or custom topics (user-defined).

• Event Subscriptions: Define what events to listen for and which endpoint to send them to.

• Event Handlers: Destinations that process events like Azure Functions, Logic Apps, Event Hubs, Service Bus, or custom webhooks.

• Event Domains: Manage event routing for multiple tenants or sources at scale.

• System Topics: Automatically created by Azure for events coming from Azure resource providers (e.g., Blob storage events).

• Custom Topics: User-created topics to which custom sources can publish events, enabling event routing for non-Azure or custom applications.

Intermediate Interview Questions and Answers

• Transport uses TLS for encryption in transit.

• Support for private endpoints (Azure Private Link) for restricting access to within virtual networks.

• Event subscriptions can include validation of endpoints and access controls.

• Using managed identities and Azure AD for secure authentication.

Advanced and Tricky Interview Questions and Answers

• Event Grid: Best for reactive event-routing for discrete, reactive events (e.g., resource changes, webhook-style events) with filtering and lightweight delivery.

• Event Hubs: Designed for big data, event streaming, telemetry ingestion with high throughput and partitioned log storage, suitable for streaming analytics.

• Service Bus: Enterprise-grade messaging broker supporting advanced messaging features like queues, topics, sessions, and transactions, suited for complex message workflows.

[FunctionName("ProcessEventGridEvent")]
public static void Run([EventGridTrigger] EventGridEvent eventGridEvent, ILogger log)
{
    log.LogInformation($"Event received: {eventGridEvent.EventType}");
    // Process event data
}

Scenario-Based Interview Questions and Answers