DOP-C02 Resilient Cloud Solutions Practice Question
A company runs a high-traffic web application on a fleet of EC2 instances behind an Application Load Balancer (ALB) with Auto Scaling. The application uses an Amazon RDS for PostgreSQL database. Recently, during a traffic spike, the application became unresponsive. Investigation revealed that the database CPU utilization reached 100%, causing queries to timeout. The Auto Scaling group added more EC2 instances, which only increased the load on the database. The DevOps team needs to implement a solution that prevents the database from being overwhelmed during traffic spikes while maintaining application availability. The solution must be cost-effective and require minimal changes to the application code. Which solution should the DevOps team implement?
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 Amazon RDS Proxy between the application and the database to pool and reuse connections.
RDS Proxy manages database connections efficiently, reducing the number of connections and CPU overhead. It also provides connection pooling, which helps handle spikes without overwhelming the database.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Implement read replicas for the RDS database and modify the application to use read replicas for read queries.
Why it's wrong here
Read replicas only offload read-only queries to separate database engines; they do not reduce the number of connections hitting the primary RDS instance. If the CPU overload stems from connection churn and write-heavy traffic, replicas require application-level read/write splitting and still leave the primary vulnerable to connection exhaustion. RDS Proxy, by contrast, multiplexes many client connections into a small pool of persistent database connections, directly addressing the root cause.
- ✗
Increase the instance size of the RDS database to a larger instance type to handle more connections.
Why it's wrong here
Scaling the RDS instance to a larger type raises the max_connections limit because it is tied to memory, but this is expensive and typically requires a downtime window during the modification. It also does not reduce the overhead of creating and destroying connections—it just postpones the connection limit being hit. RDS Proxy increases effective connection capacity without vertical scaling or an outage by reusing established database connections.
- ✓
Use Amazon RDS Proxy between the application and the database to pool and reuse connections.
Why this is correct
Amazon RDS Proxy presents a single endpoint to the application while pooling and reusing database connections on the backend, dramatically cutting the CPU and memory load caused by connection handling. It is fully managed and transparent, and during Multi-AZ failovers it can keep connections warm for faster recovery. For a high-traffic web fleet, this directly mitigates CPU exhaustion due to connection volume, making it the most efficient and cost-effective option.
- ✗
Configure Auto Scaling to launch EC2 instances based on a custom metric that tracks database CPU utilization, and throttle the number of instances.
Why it's wrong here
Adding EC2 instances based on database CPU and then throttling the fleet does not solve the connection-management problem; more application instances usually open more database connections, increasing the load on RDS. A custom CloudWatch metric is a reasonable scaling signal, but aggressive throttling caps web-tier capacity and risks availability. RDS Proxy absorbs connection spikes by multiplexing client connections, whereas auto scaling only alters the number of potential clients.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-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 DOP-C02 exam.