Azure AZ-204 Event Grid and Hubs Guide

This lesson is about not confusing Azure’s two major event-based patterns. Microsoft expects you to separate reactive event routing from large-scale event ingestion and streaming. If you read the stem too quickly, both can look like “event-driven architecture,” but they solve very different problems.

What Azure is really testing here

Use this lesson to answer one question first: is the system mainly reacting to events, or is it mainly ingesting and retaining a stream for consumers?

• Use Event Grid when the stem is about routing events to handlers when something happened.
• Use Event Hubs when the stem is about ingesting high volumes of events or telemetry for downstream consumers.
• Expect the exam to mix these with Service Bus or Queue Storage so you have to separate pub/sub event routing from durable message processing.

Fast event chooser

Event Grid versus Event Hubs

    flowchart LR
	  A["Event happens"] --> B{"What is the real need?"}
	  B -->|Route to handlers when something changed| C["Event Grid"]
	  B -->|Ingest large streams for downstream consumers| D["Event Hubs"]
	  C --> E["Functions, Logic Apps, webhooks, queues, topics, Event Hubs"]
	  D --> F["Partitions, consumer groups, retained event stream"]

How strong AZ-204 answers usually reason

1. Ask whether the event should immediately fan out to handlers or be captured as a stream.
2. If the key idea is reaction to a change, choose Event Grid.
3. If the key idea is ingesting many events for later or parallel consumers, choose Event Hubs.
4. If the stem then shifts into retries, workflows, dead-lettering, or queue-style business processing, that is usually the separate message-based lane.

Common traps

Harder scenario question

A platform receives telemetry from many devices and must let several analytics consumers read the event stream independently. At the same time, some resource-change notifications should trigger near-real-time handlers. The strongest answer usually separates the lanes: Event Hubs for large-scale ingestion and independent consumers, and Event Grid for reactive routing when something changed.

Decision order that usually wins

1. First classify the requirement as reactive event routing or retained high-throughput event ingestion.
2. If something changed and interested handlers should react, think Event Grid.
3. If events arrive at high volume and multiple consumers need to read the stream independently, think Event Hubs.
4. If routing and buffering are both needed, separate the routing signal from the downstream streaming destination.
5. Keep event notification and event stream ingestion in different buckets.

Quiz