Aurora Read Replica for Scalability and Cost

SAA-C03 By islever Editorial Last updated

Determine high-performing and/or scalable network architectures.

Short answer

C Create an Aurora read replica to offload read-only queries, preserving write performance on the primary cluster.

Question

A company that runs its application on AWS uses an Amazon Aurora DB cluster as its database. During peak usage hours when multiple users access and read the data, the monitoring system shows degradation of database performance for the write queries. The company wants to increase the scalability of the application to meet peak usage demands. Which solution will meet these requirements MOST cost-effectively?
  1. Create a second Aurora DB cluster. Configure a copy job to replicate the users’ data to the new database. Update the application to use the second database to read the data.
  2. Create an Amazon DynamoDB Accelerator (DAX) cluster in front of the existing Aurora DB cluster. Update the application to use the DAX cluster for read-only queries. Write data directly to the Aurora DB cluster.
  3. Create an Aurora read replica in the existing Aurora DB cluster. Update the application to use the replica endpoint for read-only queries and to use the cluster endpoint for write queries. Correct Answer
  4. Create an Amazon Redshift cluster. Copy the users' data to the Redshift cluster. Update the application to connect to the Redshift cluster and to perform read-only queries on the Redshift cluster.

Key Takeaways

The question tests the ability to decouple read and write workloads in Aurora; the common trap is selecting a cache layer like DAX which is intended for DynamoDB, not Aurora.

This page explains how to resolve Amazon Aurora write performance degradation caused by high read load using cost-effective scaling strategies. It establishes that adding an Aurora Read Replica is the optimal solution for offloading read-only queries while keeping write operations on the primary cluster.

Common mistake: Many learners incorrectly choose Option B (DAX) because they associate 'performance improvement' with caching, failing to recognize that DAX is specifically designed for Amazon DynamoDB and does not integrate with Aurora.

Expert Analysis

Why the Answer Is Correct

The scenario describes a situation where high read traffic is impacting the performance of write queries on an Amazon Aurora DB cluster. The most direct and cost-effective way to handle this is to offload the read-only traffic to additional nodes. Creating an Aurora Read Replica allows the application to send read queries to the replica endpoint, leaving the primary cluster free to handle writes efficiently. This matches Objective 3.4 regarding scalable network/database architectures.

Why the Other Options Are Wrong

Option A suggests creating a second full cluster for replication, which is unnecessarily complex and costly compared to a simple read replica. Option B proposes using DynamoDB Accelerator (DAX), but DAX is a caching service exclusively for Amazon DynamoDB, not Aurora RDS; it cannot cache data from Aurora. Option D suggests moving reads to Amazon Redshift, which is a data warehousing tool for analytics, not a suitable replacement for operational transactional reads in an application architecture.

Community Comment Notes

Community consensus strongly supports Option C, with users noting that read replicas are the standard mechanism for handling multiple readers. As user ug56c noted, "read queries are slowing down write queries -> we need to optimize for read queries -> we need to add read replicas." Another user, mk168898, highlighted the distinction between services, stating, "Saw that DAX is for Dynamo DB which is different from the question Aurora DB," confirming why Option B was rejected.

Official Reference

https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Aurora.Managing.Performance.html#Aurora.Managing.Performance.ReadScaling

This link opens the official vendor documentation in a new tab.

Exam Strategy

When you see 'read queries affecting write performance' in Aurora or RDS questions, immediately look for 'Read Replica' as the solution. Be careful not to confuse caching solutions (like ElastiCache or DAX) with database-native scaling mechanisms unless the source database explicitly supports them.

Frequently Asked Questions

Why can't I use DAX for Aurora?

DAX is a caching service built specifically for Amazon DynamoDB. It cannot connect to or cache data from Amazon Aurora or other RDS databases.

Is a Read Replica more cost-effective than a second cluster?

Yes. A Read Replica shares the same underlying storage infrastructure as the primary instance (in some configurations) or is simply a lighter-weight copy, making it significantly cheaper and faster to provision than a whole new secondary cluster.

More SAA-C03 FAQ →

Community Votes

C
100%

100% of anonymous learners picked answer C. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

  1. ug56c 👍 4
    Answer C, wording is that read queries are slowing down write queries -> we need to optimize for read queries -> we need to add read replicas. https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Aurora.Managing.Performance.html#Aurora.Managing.Performance.ReadScaling
  2. KennethNg923 👍 4 Answered C
    Read Replica for multiple users access and read the data
  3. Scheldon 👍 2 Answered C
    AnswerC A - We can create only RO replica of DB hence this is not possible. D - Redshift is not for a DB from my understanding but more like analitics tools B - Could be a thinkg but there is no point of Read-Only from DAX and write to DB cluster. beside it is hard to say if it would be cost effective as we are paying per hour not R/W requests as it is with replica. Hence I would go with C
  4. mk168898 👍 2
    I was thinking between B and C. Saw that DAX is for Dynamo DB which is different from the question Aurora DB. So i picked C
  5. sheilawu 👍 1 Answered B
    write queries=>High performance of read & Write Dynamo, I think DAX is a better solution.

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