AZ-900 Describe Azure architecture and services Practice Question
An e-commerce application needs to handle sudden traffic spikes during flash sales while maintaining consistent performance. Which combination of Azure services BEST addresses this requirement?
⚠ Common exam trap
Test-takers frequently confuse Azure Front Door (global HTTP/S load balancer with autoscaling support) with Azure Traffic Manager (DNS-only router that cannot scale backend resources), leading them to pick Option C.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Front Door with autoscaling backend
Azure Front Door provides global load balancing and traffic acceleration with built-in SSL offload and path-based routing, while its autoscaling backend (e.g., Virtual Machine Scale Sets or App Service) automatically adds or removes instances based on CPU or request metrics. This combination ensures that sudden traffic spikes during flash sales are absorbed without manual intervention, maintaining consistent performance and high availability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Azure Load Balancer with manual VM scaling
Why it's wrong here
Azure Load Balancer is a Layer-4 network load balancer that distributes TCP/UDP traffic among VMs within a single region and performs health probes, but it has no cross-region failover, no caching, and no application-layer intelligence. Manual VM scaling requires an operator to observe a bottleneck and then initiate creation or startup of VMs, which takes minutes or even hours. A sudden spike can saturate capacity before anyone reacts, causing dropped connections and downtime. Because Load Balancer itself cannot autoscale, it cannot respond to demand changes at the speed that real-time traffic bursts require.
- ✓
Azure Front Door with autoscaling backend
Why this is correct
Azure Front Door provides global, layer-7 load balancing via anycast delivery, directing users to the nearest edge location and caching static content to reduce origin requests. Dynamic requests are forwarded to an origin protected by an autoscaling rule, which provisions or decommissions backend instances based on real-time CPU or request metrics. Autoscaling ensures that demand spikes are absorbed automatically without manual intervention, making this combination the only one that both optimizes global traffic and scales compute to match workload surges.
- ✗
Azure Traffic Manager with static VMs
Why it's wrong here
Azure Traffic Manager performs DNS-level routing only, sending clients to different regional endpoints based on latency or priority, but it never inspects HTTP requests and cannot cache content at the edge. A fleet of static VMs has no autoscaling, so when traffic spikes exceed the total VM capacity, requests will time out or fail regardless of how Traffic Manager routes them. It also cannot offload compute or dynamically add instances, meaning any surge directly overwhelms the fixed-capacity backends. Thus Traffic Manager merely distributes load among static resources; it provides no elasticity or absorption of demand spikes.
- ✗
Azure CDN alone
Why it's wrong here
A pure Azure CDN only caches static, edge-served assets like images, stylesheets, JavaScript, and video; dynamic requests, APIs, and authenticated content are proxied straight to the origin. The CDN does not scale or monitor the origin pool, so a spike in dynamic traffic hits the same limited web servers and causes performance degradation. It also offers no cross-region health-based load balancing among multiple origins beyond simple origin failover. Consequently, CDN alone protects static delivery but leaves compute capacity and application availability vulnerable to traffic bursts.
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
High availability
High availability is a system design approach that aims to keep applications and services operational and accessible with minimal downtime, even when some components fail.
Key term
Azure Front Door
Azure Front Door is a global cloud load balancer and content delivery network that routes user traffic to the fastest and most available backend application across multiple regions.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-900 exam.