AZ-900 Describe cloud concepts Practice Question
A retail company runs its e-commerce platform on a public cloud. During a major sale event, they want to ensure that the application remains accessible even if an entire data center fails. Which cloud computing concept does this describe?
⚠ Common exam trap
A common mix-up: candidates confuse high availability with disaster recovery, but high availability is about real-time failover to maintain uptime, while disaster recovery is about restoring service after a major outage, often with data loss or downtime.
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
✓
High availability
High availability ensures that the application remains accessible even if an entire data center fails, typically through redundant infrastructure across multiple availability zones. This is achieved by deploying the application in a load-balanced, multi-AZ configuration that automatically fails over to healthy instances, maintaining uptime despite a complete data center outage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Scalability
Why it's wrong here
Scalability is the ability of a system to handle increased load by adding resources, either vertically (increasing CPU/RAM of a single instance) or horizontally (adding more instances), often based on both demand and threshold rules. While scaling out can increase capacity and potentially create multiple copies of a workload, it does not by itself guarantee continuous operation if one component fails. For instance, if all instances depend on a single un-replicated database or storage account, a failure in that component will still cause downtime despite scalability.
When this WOULD be correct
A question like 'A company expects a sudden spike in traffic during a product launch and needs to automatically add virtual machines to handle the load. Which concept does this describe?' would make scalability the correct answer.
- ✗
Elasticity
Why it's wrong here
Elasticity is the capability of a cloud system to automatically add or remove compute, storage, or network resources in response to real-time changes in demand, such as a sudden spike in web traffic. This is a capacity-management mechanism, often implemented via Azure Autoscale, and it does not inherently provide fault tolerance. An elastic workload can still experience downtime if a single virtual machine or service fails because elasticity alone does not include failover or redundancy mechanisms.
- ✓
High availability
Why this is correct
High availability is a design principle that minimizes application downtime by eliminating single points of failure and enabling automatic failover when a component fails. This is achieved through redundancy (multiple instances, Azure Availability Zones, or Availability Sets), health probes, and load balancers that reroute traffic to healthy replicas. In the e-commerce scenario, HA ensures the platform remains reachable and functional during a component failure, directly addressing the stated requirement to keep services running.
- ✗
Disaster recovery
Why it's wrong here
Disaster recovery is a strategy for restoring an entire workload or data center after a catastrophic event, such as a regional outage, cyberattack, or natural disaster, using backups and replication to a secondary location. It is measured by recovery time objective (RTO) and recovery point objective (RPO), which typically allow for minutes to hours of downtime. Unlike HA, DR does not prevent interruption during a component failure; it only recovers operations after the fact, making it unsuitable for the scenario that demands minimal downtime during a localized fault.
When this WOULD be correct
A question that asks: 'A company wants to restore its e-commerce platform after a major outage with minimal data loss and downtime. Which concept describes this plan?' would make disaster recovery correct, as it involves processes for recovery after a disaster.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓High availabilityCorrect answer▾
Why this is correct
High availability is a design principle that minimizes application downtime by eliminating single points of failure and enabling automatic failover when a component fails. This is achieved through redundancy (multiple instances, Azure Availability Zones, or Availability Sets), health probes, and load balancers that reroute traffic to healthy replicas. In the e-commerce scenario, HA ensures the platform remains reachable and functional during a component failure, directly addressing the stated requirement to keep services running.
✗ScalabilityWrong answer — click to see why▾
Why this is wrong here
Scalability refers to the ability to increase or decrease resources to handle load changes, not to maintain availability during a data center failure. The question specifically asks about ensuring application accessibility despite an entire data center failing, which is a high availability concern.
★ When this WOULD be the correct answer
A question like 'A company expects a sudden spike in traffic during a product launch and needs to automatically add virtual machines to handle the load. Which concept does this describe?' would make scalability the correct answer.
Why candidates choose this
Candidates may confuse scalability with high availability because both involve handling increased demand, but scalability focuses on resource adjustment, not fault tolerance.
✗Disaster recoveryWrong answer — click to see why▾
Why this is wrong here
Disaster recovery focuses on restoring IT infrastructure and data after a disaster, not on maintaining continuous availability during a failure. The question asks for ensuring the application remains accessible during a data center failure, which is high availability, not recovery after an outage.
★ When this WOULD be the correct answer
A question that asks: 'A company wants to restore its e-commerce platform after a major outage with minimal data loss and downtime. Which concept describes this plan?' would make disaster recovery correct, as it involves processes for recovery after a disaster.
Why candidates choose this
Candidates may confuse disaster recovery with high availability because both deal with failures, but disaster recovery is about recovery after an outage, not maintaining uptime during one.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
What is Cloud Computing?
Key term
Availability
Availability is the measure of how often a system or service is operational and accessible when needed, typically expressed as a percentage of uptime.
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.
About these practice questions
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JA
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.