AZ-900 Describe cloud concepts Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  Vertical scaling adds more instances; horizontal scaling increases instance size

  Why it's wrong here

  This statement reverses the actual definitions. Vertical scaling, or scaling up, means increasing the size or capacity of a single resource, such as adding more vCPUs, RAM, or disk to one virtual machine. Horizontal scaling, or scaling out, means adding more instances of that resource, usually behind a load balancer to distribute traffic. Because the option swaps these fundamental meanings, it is incorrect.

• ✓

  Vertical scaling increases a single resource's capacity; horizontal scaling adds more instances

  Why this is correct

  This accurately describes the two primary scaling strategies in cloud computing. Vertical scaling (scaling up/down) increases or decreases the capacity of a single resource, such as moving a virtual machine to a larger SKU with more CPU and memory, which often requires a restart and has hardware limits. Horizontal scaling (scaling out/in) adds or removes additional instances of a resource, such as placing multiple VMs or containers behind a load balancer, and enables elasticity, redundancy, and near-unlimited growth via distributed architecture. Azure implements this with capabilities like VM scale sets and App Service autoscaling.

• ✗

  Both vertical and horizontal scaling achieve the same result through different means

  Why it's wrong here

  Although both methods are used to handle increased demand, they are not functionally identical. Vertical scaling often requires stopping the resource to resize it, introduces downtime, and is ultimately bounded by the largest available hardware; horizontal scaling, by contrast, adds new instances and can scale out indefinitely, providing redundancy and better fault tolerance. These differences in availability, cost, operational complexity, and maximum capacity mean the outcomes and trade-offs are not the same.

• ✗

  Vertical scaling is for storage; horizontal scaling is for compute

  Why it's wrong here

  This option incorrectly classifies scaling approaches by resource type. Both vertical and horizontal scaling apply across compute, storage, and other services: you can vertically scale a VM by enlarging its managed disk or horizontally scale stateless web servers by deploying more instances. The real distinction is whether you increase a single resource's capacity or add more replicas, not whether the resource is storage or compute.

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