One of the key features that Event Grid provides is the durable delivery of the events that it manages. Event Grid assures you that every message it manages will be delivered, at least once, for each subscription.
Every time an event is received on one of its topics from Event Grid, it will be sent immediately to the corresponding registered endpoint and then to the subscription registered for that endpoint.
If the endpoint doesn't return the acknowledgment for the event (that is, if the event isn't delivered correctly to the subscription), Event Grid will try to deliver the event again.
By default, Event Grid waits for 30 seconds for a timeout after sending an event to an endpoint; then, if the endpoint doesn't respond or responds with an error, Event Grid puts the event in the retry queue.
The retry policy is, as usual...
