SAP-C02 Design for New Solutions Practice Question
A company is designing a new multi-region disaster recovery solution for a critical application running on AWS. The primary region is us-east-1. The application uses Amazon RDS for MySQL with Multi-AZ, and runs on EC2 instances behind an ALB. The RPO must be less than 5 minutes, and RTO less than 30 minutes. The company wants to minimize costs when the DR solution is not in use. Which solution should a Solutions Architect recommend?
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
✓
Set up an RDS MySQL cross-Region read replica in us-west-2. Keep a standby EC2 environment with Auto Scaling configured to scale from 0 to minimum instances using a CloudWatch alarm on health checks. Use Route 53 failover routing to switch DNS to us-west-2.
Option D meets the RPO of less than 5 minutes because RDS cross-Region read replicas use asynchronous replication with a typical lag of seconds. It meets the RTO of less than 30 minutes because the read replica can be promoted to a standalone primary in minutes. The standby EC2 environment with Auto Scaling set to 0 (scaling up based on health check alarms) minimizes cost when not in use. Route 53 failover routing redirects traffic to us-west-2 after promotion. Option A is incorrect because a single hot standby EC2 instance incurs ongoing cost, and it does not meet the cost minimization requirement. Option B is incorrect because automated snapshots have an RPO of up to 24 hours (not <5 minutes), and restoring to S3-mounted volumes is not a functional database serving solution. Option C is incorrect because Multi-AZ in both regions is costly (always running instances) and cross-Region load balancing with ALB is not a native feature for failover; plus Multi-AZ does not provide a separate read replica in another region for DR without additional replication.
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 RDS MySQL with cross-Region read replicas in us-west-2. Use a hot standby EC2 environment with a single instance. Use Route 53 failover routing.
Why it's wrong here
A single EC2 instance is a single point of failure; read replicas are for read scaling, not automatic failover.
- ✗
Back up RDS MySQL to S3 using automated snapshots and copy them to us-west-2. Use EC2 instances with S3-mounted volumes to serve traffic from the backup.
Why it's wrong here
Snapshot backup RPO can be up to 24 hours; restoring from S3 is slow, RTO will exceed 30 minutes.
- ✗
Use RDS MySQL with Multi-AZ in us-east-1 and a second Multi-AZ deployment in us-west-2. Keep EC2 instances running in us-west-2 behind an ALB with cross-Region load balancing.
Why it's wrong here
Multi-AZ is within a region; cross-Region load balancing is not a native feature; keeping instances running incurs cost.
- ✓
Set up an RDS MySQL cross-Region read replica in us-west-2. Keep a standby EC2 environment with Auto Scaling configured to scale from 0 to minimum instances using a CloudWatch alarm on health checks. Use Route 53 failover routing to switch DNS to us-west-2.
Why this is correct
Cross-Region read replicas provide low RPO; scaling from 0 minimizes cost; Route 53 failover provides RTO.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 practice question is part of Courseiva's free Amazon Web Services 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 SAP-C02 exam.