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Event grid are used for Event distribution (React to status changes) not for the messages. You can refer to compare messaging services for more details.
If you want to leverage the event grid now the flow will be:
Sender application sends message to service bus --> Create Event Grid subscription on your service bus resource (endpoint configured as webhook of AKS web API) --> AKS will have the web API that listens to the request and in web API you need to use service bus SDK to consume the message.
Note: Service Bus Premium SKU is only supported with the eventgrid system topics.
You can refer to similar document on azure function for Respond to Azure Service Bus events received via Azure Event Grid by using Azure Functions. Instead of azure function you need to create AKS webservice that will be used as webhook endpoint on your event grid subscription.
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