Memory hook: Start with constraints and ownership; pick services only after defining the boundaries.
Must remember
- Translate business needs into SLOs, RPO/RTO, latency, data residency, identity, consistency, budget and operating-skill constraints. Azure Well-Architected considers reliability, security, cost optimisation, operational excellence and performance efficiency. Cloud Adoption Framework/landing zones address organisation-wide adoption and governance.
- Design tenant/subscription/management-group boundaries, privileged access, policy and central evidence. Managed identities reduce secret handling; directory roles, resource roles and data permissions remain distinct. Centralised services need resilience and a clear owner.
- Choose VM versus managed app/container/serverless hosting by required control, execution pattern, scaling and operating burden. AKS is useful for Kubernetes requirements but adds platform responsibilities. Event-driven designs need retry, idempotency, poison-message and backpressure handling.
- Service Bus handles brokered queues/topics and enterprise messaging; Event Grid distributes events; Event Hubs ingests high-volume streams; Logic Apps orchestrates integrations; Functions performs event-driven code; API Management governs API exposure. Do not substitute a notification bus for every durable work queue.
- Network choices include hub/spoke, Virtual WAN, peering, VPN/ExpressRoute, private endpoints and central inspection. Determine address space, DNS, route propagation, public/private access and transfer costs. Application Gateway, Front Door and Traffic Manager solve different delivery problems.
- Migration begins with inventory/dependency discovery, Azure Migrate assessment and a business case. Rehost, replatform, refactor or replace according to constraints; select suitable data-migration tools and staged cutover. Validate licences, capacity and rollback before retiring the source.
Choose under exam pressure
| Requirement | Choice and reason |
|---|---|
| Strict OS/custom-agent requirement | VM-based hosting may be justified. |
| Managed enterprise messaging with subscriptions | Service Bus topics/subscriptions. |
| Organisation-wide resource constraints | Landing-zone governance with Policy and scoped access. |
Traps
- A cloud service name is not an architecture justification.
- Centralisation can increase blast radius and transfer cost.
- An Expert credential has prerequisites beyond one exam.
Active recall
1. What must precede service selection?
Explicit functional/nonfunctional requirements, constraints and operating ownership.
2. Why might AKS be the wrong choice for one small web app?
Its additional platform complexity may not be justified by the requirements.
3. Which messaging service fits a replayable high-volume event stream?
Event Hubs, with suitable partitioning and consumer design.
4. Why assess dependencies before migration waves?
A moved component may still rely on an unreachable or incompatible service.
5. What makes a landing zone useful?
Repeatable identity, network, governance and operational foundations for workloads.