CV0-004 Cloud Architecture and Design Practice Question
A cloud architect is designing a multi-tier application that must be resilient to the failure of a single availability zone. The application consists of a web tier, an application tier, and a database tier. Which TWO design decisions will help achieve this resilience? (Choose two.)
⚠ Common exam trap
The trap here is focusing only on the compute tiers and forgetting that the database tier also needs a multi-AZ strategy to achieve full resilience.
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
✓
Deploy the web and application tiers across multiple availability zones and use a load balancer to distribute traffic.
To be resilient to a single availability zone failure, both the stateless tiers and the stateful database tier must be distributed. Deploying the web and application tiers across multiple zones behind a load balancer ensures continued service if one zone fails. Configuring the database with a multi-AZ standby replica provides automatic failover for the data layer. Together, these decisions eliminate single points of failure across all tiers.
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 single, large database instance in one availability zone with frequent snapshots.
Why it's wrong here
A single database instance in one zone is a single point of failure. If that zone becomes unavailable, the database is inaccessible until the instance is restored from a snapshot, which can take significant time. Snapshots are for backup and recovery, not for high availability. This design does not meet the requirement of resilience to a single availability zone failure.
- ✗
Place all tiers in a single availability zone to reduce network latency between components.
Why it's wrong here
While placing all tiers in one zone can reduce latency, it creates a single point of failure. If that zone fails, the entire application becomes unavailable. The requirement is to be resilient to the failure of a single availability zone, so spreading tiers across zones is necessary. Latency optimization should not compromise availability in this scenario.
- ✓
Deploy the web and application tiers across multiple availability zones and use a load balancer to distribute traffic.
Why this is correct
Distributing the web and application tiers across multiple availability zones ensures that if one zone fails, the remaining zones can continue to serve requests. A load balancer health-checks instances and routes traffic only to healthy targets. This eliminates single points of failure at the compute layer and is a fundamental practice for zone-resilient architectures.
- ✓
Configure the database tier with a multi-AZ standby replica that can be promoted in the event of a failure.
Why this is correct
A multi-AZ standby replica maintains a synchronous copy of the database in a different availability zone. If the primary zone fails, the standby can be promoted automatically or manually, allowing the database tier to recover. This provides high availability for the data layer, which is essential because databases are often stateful and cannot be simply replicated like stateless tiers.
- ✗
Store all session state on the local disk of each web server to improve performance.
Why it's wrong here
Storing session state locally ties users to a specific server. If that server or its availability zone fails, the session data is lost and users are disrupted. For a resilient multi-AZ design, session state should be externalized to a shared, replicated store such as a database or a distributed cache. Local disk storage is not zone-resilient and defeats the purpose of multi-AZ deployment.
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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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