Azure Event Grid

Azure Event Grid is a fully managed event routing service built on a publish-subscribe model. It enables event-driven architectures by connecting event sources (publishers) to event handlers (subscribers) with reliable delivery, filtering, and fan-out. Event Grid is a key building block in Azure serverless architectures, providing the glue between services.

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Events vs Messages

Before diving into Event Grid, it is important to understand the difference between events and messages:

Characteristic	Event	Message
Purpose	Notification that something happened	Command or data transfer
Content	Lightweight — describes what happened	Contains the full payload
Expectation	Publisher does not expect a specific action	Sender expects the message to be processed
Coupling	Loose — publisher does not know the subscribers	Tighter — sender knows the receiver
Example	"Blob uploaded to container"	"Process this order"

Event Grid handles events. Service Bus and Queue Storage handle messages. Choose the right service based on whether you are notifying or commanding.

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How Event Grid Works

The architecture has four components:

1. Event Sources (Publishers)