CV0-004 Cloud Architecture and Design Practice Question
A cloud architect is designing a highly available three-tier application on AWS. The web tier must survive the loss of a single Availability Zone, and the database tier must support automatic failover with minimal administrative intervention. Which TWO design decisions should the architect implement? (Choose two.)
⚠ Common exam trap
The trap here is equating backups or larger instances with high availability, when neither provides automatic failover during a zone outage.
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
✓
Use a Multi-AZ deployment for Amazon RDS so a standby is maintained in a second Availability Zone
Zone-level resilience for the web tier comes from distributing instances across zones behind a load balancer, and database resilience with automatic failover comes from a Multi-AZ standby that is promoted without manual steps. The remaining choices either concentrate risk in one zone, rely on slow manual restoration, or depend on human intervention during an 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.
- ✓
Use a Multi-AZ deployment for Amazon RDS so a standby is maintained in a second Availability Zone
Why this is correct
RDS Multi-AZ maintains a synchronous standby in another Availability Zone and automatically promotes it during a failure, updating the DNS endpoint so the application reconnects without manual intervention. This satisfies the database requirement for automatic failover with minimal administration.
- ✗
Configure Amazon RDS as a Single-AZ instance with automated snapshots every hour
Why it's wrong here
Snapshots provide point-in-time recovery but require manual restoration into a new instance, which takes far longer than automatic failover and involves administrative effort. A Single-AZ instance has no standby to promote, so a zone failure causes extended downtime and does not meet the automatic failover requirement for the database tier.
- ✗
Attach an Elastic IP address to each web server instance and update DNS manually during an outage
Why it's wrong here
Elastic IPs and manual DNS updates introduce human intervention and delay during an incident, and they do not by themselves create redundant capacity in another zone. This approach also scales poorly and risks misconfiguration, so it does not deliver the automated, zone-resilient design the scenario requires.
- ✗
Place all web servers in a single Availability Zone and use larger instance types
Why it's wrong here
Larger instances improve capacity but do not provide fault isolation, because a zone-level failure still takes down every instance in that zone. Consolidating into one Availability Zone increases the blast radius and contradicts the requirement that the web tier survive the loss of a single zone, so this decision should not be implemented.
- ✓
Deploy web servers in an Auto Scaling group spanning at least two Availability Zones behind an Application Load Balancer
Why this is correct
Spreading the Auto Scaling group across multiple Availability Zones and fronting it with an Application Load Balancer means the load balancer routes only to healthy targets, so losing one zone removes those instances from rotation while the others continue serving traffic. This directly provides the zone-level resilience required for the web tier.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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