Quick Note — Recommend an Event-Driven Architecture
AZ-305 › Unit 4: Design infrastructure solutions › Design an application architecture › Recommend an event-driven architecture
Quick Note — Recommend an Event-Driven Architecture
A bank's payments team migrates an aging batch reconciliation pipeline to "modern microservices". The first design is twelve services calling each other over HTTP — a service-oriented architecture in name only. Two months in, every change to one service breaks two others, latency creeps up as the call depth grows, and a single slow dependency takes down the whole chain. The architect proposes a structural redesign: each service publishes domain events to an event backbone, and downstream services subscribe to the events they care about. Two months later the team ships features independently, latency drops, and a slow service degrades only its own work — not the front door.…
Retrieval target
- Recommend an Event-Driven Architecture
- Closed-book recall
- 5 minutes
- Open the full lesson after a miss
Decision anchors
| Prompt | Compact answer |
|---|---|
Azure Event Grid | A push-based event-routing service for discrete state-change events. Sources publish events; Event Grid routes to subscribed handlers (Functions, Logic Apps, webhooks, Event Hubs). Native system topics for Azure services (Storage blob created, RG deployment complete, Resource modified, AKS health). Custom topics for app-generated events. At-least-once delivery, 24-h retry, DLQ to Blob. |
Azure Event Hubs | A big-data streaming ingest service. Ingests millions of events/second; events sit in partitions (ordered, append-only logs), retained up to 1 day (Basic), 7 days (Standard) or 90 days (Premium / Dedicated); Capture copies events to Blob Storage or Data Lake Storage but does not extend how long they stay readable in the hub. Pull-based consumers (consumer groups). Use for telemetry firehose, app logs, IoT, click streams — anything where each event is small but volume is huge. |
| Event Grid system topic vs custom topic | System topic — Azure-emitted events from a specific resource (Storage account 'BlobCreated', Subscription 'ResourceWriteSuccess', AKS, ACR, etc.). Auto-created when you subscribe. Custom topic — you create the topic, your apps publish events to it via SDK / REST. Subscribers can be any Event Grid handler. Use custom topics to publish your own domain events ('OrderPlaced', 'CustomerSignedUp'). |
Event Hubs Partition and Consumer Group | Partition — an ordered, append-only log of events. Producers route events via a partition key; events with the same key always land in the same partition (preserves per-key order). Partition count is set per event hub at creation, not per namespace — max 32 (Basic / Standard), 100 per event hub on Premium (capped at 200 per PU across the namespace), $1,024 per event hub on Dedicated. Only Premium and Dedicated can increase the count after creation, and never decrease it. Consumer Group — a logical view of the stream; each consumer group has its own checkpointed read position.… |
Read the answers once, then cover the right-hand column and reconstruct each one from the prompt. A useful answer names the requirement, the recommended control or service boundary, and the nearest alternative it rejects. If you can only recognize the answer after seeing it, retrieval is not yet secure.
Ninety-second explanation
Without notes, explain:
- What requirement signals this learning objective rather than a neighbouring one?
- Which two solution families are most likely to be compared?
- Which hard constraint eliminates the strongest distractor?
- What identity, network, data, or failure boundary must appear in the design?
- Which operational test would prove the recommendation works?
Then compare your explanation with the full lesson. Record the missing decision rule—not merely the missed product name—in your error log.
When to open the full lesson
Open the curriculum-linked lesson when you cannot explain a comparison, when a scenario depends on a numeric limit or SKU feature, or when the service is on a retirement path. Use current Microsoft Learn documentation for availability, limits, pricing, naming, and migration milestones; the quick note is intentionally compact.
Source and freshness
Derived from the linked AZ-305 lesson and retrieval deck, grounded in both attached course sources. Reviewed 2026-08-02. Current Microsoft documentation controls changing product contracts.