RDS Read Replicas: Offloading Read Traffic
A company is using an Amazon RDS for MySQL database for an e-commerce application. During a sales event, the database experiences high read traffic, causing slow query performance. The company wants to reduce the read load on the primary database without changing the application code. Which solution meets these requirements?
Quick Answer
The answer is to create an Amazon RDS read replica and direct read traffic to it. This solution is correct because a read replica is an asynchronous copy of the primary database that can handle SELECT queries, effectively offloading read traffic without requiring any changes to the application code—the application simply needs to point its read operations to the replica’s endpoint. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of scaling strategies for managed databases, often appearing alongside traps like ElastiCache (which demands code modifications) or Multi-AZ (which only provides failover, not read scaling). A common mistake is confusing read replicas with Multi-AZ deployments; remember that replicas scale reads, while Multi-AZ ensures availability. Memory tip: “Replicas for reads, Multi-AZ for needs”—if your goal is to reduce read load without touching code, think replicas first.
⚠ Common exam trap
Test-takers frequently confuse Multi-AZ with read replicas, assuming Multi-AZ provides read scaling, when in fact Multi-AZ only ensures failover redundancy and does not serve read traffic.
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
✓
Create an Amazon RDS read replica and direct read traffic to it.
An Amazon RDS read replica is a read-only copy of the primary database that can offload read traffic without requiring any application code changes. By directing read queries to the replica, the primary database's load is reduced, improving performance during high-read events. This solution is specifically designed for read-heavy workloads and integrates seamlessly with existing MySQL connections.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable Multi-AZ on the RDS instance.
Why it's wrong here
Multi-AZ provides failover, not read scaling.
- ✓
Create an Amazon RDS read replica and direct read traffic to it.
Why this is correct
Read replicas handle read-only traffic, reducing load on the primary.
- ✗
Increase the instance size of the RDS database.
Why it's wrong here
Scaling up helps but may cause downtime and is less cost-effective.
- ✗
Deploy Amazon ElastiCache to cache query results.
Why it's wrong here
Requires application code changes to use the cache.
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Same concept, more angles
2 more ways this is tested on DEA-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A data engineer needs to set up a new Amazon RDS for MySQL database for a web application. The application experiences variable read traffic and requires low read latency. The engineer needs to minimize downtime during maintenance and provide read scalability. Which configuration meets these requirements?
easy- ✓ A.Multi-AZ db.r5.large instance with two Read Replicas
- B.Multi-AZ db.r5.large instance
- C.Single-AZ db.r5.large instance
- D.Single-AZ db.r5.xlarge instance
Why A: A Multi-AZ deployment provides high availability and automatic failover to minimize downtime during maintenance, while adding two Read Replicas offloads read traffic from the primary instance, reducing read latency and enabling read scalability. The db.r5.large instance size is sufficient for the variable read workload, and Read Replicas can be promoted to standalone instances if needed.
Variation 2. A company runs a critical application on Amazon RDS for MySQL. To ensure high availability and automatic failover, the database is deployed as a Multi-AZ DB instance. The application uses read-heavy workloads. Which additional configuration should be used to offload read traffic without impacting write performance?
medium- A.Use the Multi-AZ standby instance for read queries.
- ✓ B.Create one or more Read Replicas in different AZs.
- C.Use Amazon ElastiCache to cache read queries.
- D.Change to a Single-AZ deployment with a larger instance size.
Why B: Amazon RDS Read Replicas are designed to offload read traffic from the primary DB instance without affecting write performance. Unlike the Multi-AZ standby instance, which is not accessible for reads, Read Replicas can be placed in different Availability Zones and serve read queries independently, improving read scalability while the primary handles writes.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 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 DEA-C01 exam.