Azure Event Grid
What it is
Azure Event Grid is a managed publish-subscribe service that routes an event to one or more interested destinations. An event is a short notice that something happened: for example, “a blob was created” or “an order was accepted.”
Think of a building’s fire alarm. The alarm announces an event; it does not tell each person exactly what work to do. Each listener decides how to react.
Why it exists
Without Event Grid, an application might repeatedly ask another service, “Has anything changed yet?” Event Grid lets a publisher announce a change once and lets subscribers receive only the events they need. Filters can narrow a subscription, such as sending Northwind only events for new order-receipt files.
Key ideas
- An event source publishes an event. It can be an Azure service, a custom application, or a partner service.
- A topic is the address where events are published. An event subscription says which events to select and where to send them.
- An event handler is the destination that reacts, such as a webhook, Azure Function, or Event Hubs. HTTP event delivery can be push or pull, depending on the Event Grid feature and configuration.
- With push delivery, Event Grid retries failed deliveries with exponential backoff for up to 24 hours. A handler can therefore see an event more than once; make its work safe to repeat.
- Event Grid is best when the essential meaning is “this state changed; react if you care.” It is not automatically the best choice for a durable work queue or a strict, ordered business workflow.
Northwind example
Luis configures the ordering application to publish OrderAccepted after it stores an order. A subscription sends that event to a function that sends the customer a confirmation, and another subscription sends it to an analytics process. Neither subscriber has to slow down checkout. If Event Grid retries the confirmation event, the function uses the order ID to avoid sending two emails.
Event Grid and Service Bus
Both services move messages, but ask a different question:
| If the requirement is… | Usually start by considering… |
|---|---|
| “Tell several systems that something happened.” | Event Grid |
| “Hold this business task until a worker safely processes it.” | [[service-bus |
An event can trigger a Service Bus message, but the two services do not become interchangeable. Choose from the delivery, ordering, workflow, and consumer requirements—not their shared word “message.”
Common confusion
- An event is a statement about a past change, not necessarily a command such as “charge this card.” A command needs a worker, validation, and reliable processing rules.
- A successful publisher call does not prove every downstream handler completed its work. Monitor subscriptions and handle failed deliveries.
- Event Grid is not a replacement for a database. Save the business record separately; the event helps systems react to it.
Related
service-bus · event-hubs · azure-functions · function-triggers · northwind-traders-case-study
Sources and re-audit
- Microsoft Learn — What is Azure Event Grid?, checked 2026-09-16.