SAA-C03 Design Resilient Architectures Practice Question
A company runs a critical API on Amazon EC2 behind an Application Load Balancer in a single AWS Region. The business requires the API to keep serving traffic if an entire Availability Zone becomes unavailable, and the recovery must not depend on any manual step. The database is Amazon RDS for PostgreSQL configured as a Single-AZ instance. Which combination of changes should a solutions architect implement to meet these requirements?
⚠ Common exam trap
The trap here is reaching for an RDS read replica for high availability, when replicas are asynchronous and read-only and require manual promotion.
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
✓
Configure the Auto Scaling group to span at least two Availability Zones with a health check grace period, and convert the RDS instance to a Multi-AZ DB instance deployment.
Automatic recovery across an Availability Zone failure needs redundant compute and a database that fails over on its own. A multi-AZ Auto Scaling group keeps the API serving through the load balancer, and Multi-AZ RDS maintains a synchronous standby that is promoted automatically to the same endpoint, so no human action is required.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure the Auto Scaling group to span at least two Availability Zones with a health check grace period, and convert the RDS instance to a Multi-AZ DB instance deployment.
Why this is correct
Spreading the Auto Scaling group across multiple Availability Zones lets the load balancer route to healthy instances when one zone fails, and Multi-AZ RDS maintains a synchronous standby in another zone with automatic failover to the same endpoint. Together these provide automatic, hands-off recovery for both compute and database tiers.
- ✗
Enable Multi-AZ on the Application Load Balancer by adding a second listener in a different Availability Zone.
Why it's wrong here
An Application Load Balancer is already regional and requires subnets in at least two Availability Zones; adding a listener does not add zone redundancy and listeners are protocol and port configurations, not placement controls. This change does nothing for the compute or database tiers and leaves the database as a single point of failure.
- ✗
Take hourly RDS snapshots and configure an Auto Scaling lifecycle hook to restore the snapshot into a new Availability Zone during a failure.
Why it's wrong here
Snapshot restoration creates a new database instance and requires manual or scripted orchestration, and hourly snapshots can lose up to an hour of data. Lifecycle hooks act on instance termination and launch events, not on Availability Zone failures, so this design neither automates recovery nor meets the recovery point expectation.
- ✗
Create an RDS read replica in a second Availability Zone and update the application to write to the replica when the primary fails.
Why it's wrong here
A read replica is asynchronous and read-only, so it cannot accept writes without being promoted, which is a manual step. The application would also need connection-string changes and write-redirection logic, violating the no-manual-step requirement and risking data loss because replication lags behind the primary.
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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 Amazon Web Services exam blueprint
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