Event Grid: Custom Topics and Event Domains

While system topics let you react to Azure service events, custom topics allow you to publish your own events from any application. Event domains take this further by providing a single management endpoint for thousands of related topics. This lesson covers how to create and use custom topics, how to secure them, and when to use event domains for large-scale scenarios.

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Custom Topics

A custom topic is an Event Grid endpoint that you create to publish events from your own applications. Any service — a web API, a background worker, an IoT device — can send events to a custom topic using HTTP POST.

Creating a Custom Topic

az eventgrid topic create \
  --name app-events \
  --resource-group rg-messaging \
  --location uksouth \
  --input-schema eventgridschema

After creation, the topic has an endpoint URL and two access keys:

az eventgrid topic show --name app-events --resource-group rg-messaging --query "endpoint"
az eventgrid topic key list --name app-events --resource-group rg-messaging

Publishing Events

import { EventGridPublisherClient, AzureKeyCredential } from '@azure/eventgrid';

const client = new EventGridPublisherClient(
  'https://app-events.uksouth-1.eventgrid.azure.net/api/events',
  'EventGrid',
  new AzureKeyCredential(topicKey)
);