Event Grid: system and custom topics, event subscriptions, filters (event type, subject begins/ends with, advanced)

Azure Event Grid is a fully managed event routing service. It is built for reactive programming: when something happens, such as a blob being created, a resource group changing or a Key Vault secret nearing expiry, Event Grid pushes a small notification (an event) to whoever subscribed. Events describe that something happened; they are not commands or large payloads, and the publisher does not care who handles them.