SAA-C03 practice question 7 of 35

A company uses Amazon RDS (or PostgreSQL to run its applications in the us-east-1 Region. The company also uses machine learning (ML) models to…

Choose your answer, then check it against the explanation and the full breakdown below.

Domain Design Cost-Optimized Architectures

A company uses Amazon RDS (or PostgreSQL to run its applications in the us-east-1 Region. The company also uses machine learning (ML) models to forecast annual revenue based on neat real- time reports. The reports are generated by using the same RDS for PostgreSQL database. The database performance slows during business hours. The company needs to improve database performance. Which solution will meet these requirements MOST cost-effectively?

Answer options

Correct Answer:

Explanation

The core issue is performance degradation on the primary RDS database due to heavy read operations from reporting and ML workloads. The most effective and standard AWS solution for scaling read-intensive workloads on an RDS database is to create a read replica. A read replica is an asynchronously replicated, read-only copy of the primary database. By directing the reporting queries to this replica, the read load is isolated from the primary instance, which can then dedicate its resources to the main application's transactions, thus improving its performance. Creating the replica in the same region (us-east-1) is the most cost-effective option as it minimizes data transfer costs and network latency compared to a cross-Region solution.

Why Incorrect

A. A cross-Region read replica solves the read-scaling problem but incurs higher data transfer costs and network latency than an in-Region replica, making it not the most cost-effective solution.

B. A standard Multi-AZ deployment is for high availability and automatic failover, not for scaling read performance. The standby instance in a Multi-AZ DB instance deployment cannot be used to serve read traffic.

C. Using AWS DMS is overly complex and expensive for this use case. It requires provisioning and managing a separate replication instance and is designed for migrations, not for simple read scaling of an existing RDS database.

References

1. Amazon RDS User Guide

"Working with Amazon RDS read replicas": This document states

"You can reduce the load on your primary DB instance by routing read queries from your applications to the read replica. Read replicas allow you to elastically scale out beyond the capacity constraints of a single DB instance for read-heavy database workloads." This directly supports using a read replica to solve the performance issue.

2. Amazon RDS User Guide

"High availability (Multi-AZ) for Amazon RDS": The documentation clarifies the purpose of Multi-AZ: "In a Multi-AZ DB instance deployment

Amazon RDS automatically provisions and maintains a synchronous standby replica in a different Availability Zone... The standby replica can't serve read requests." This confirms that option B is incorrect for a standard Multi-AZ DB instance.

3. Amazon RDS Pricing

"Data Transfer" section: AWS pricing details show that data transfer "In from internet" is free

but data transfer "Out to internet" (which includes inter-region traffic) is priced per GB. Data transfer within the same AWS Region between Availability Zones has a lower cost. This supports the cost-effectiveness of an in-region replica (Option D) over a cross-region one (Option A).

4. AWS Database Migration Service User Guide

"What is AWS Database Migration Service?": The guide describes AWS DMS as a service for migrating databases to AWS quickly and securely

supporting both homogeneous and heterogeneous migrations. This highlights that its primary purpose is migration

making it a more complex and less direct solution than a native read replica for read scaling.

Question 7 of 35

Question breakdown

Tests: Offload read-heavy workloads from an RDS primary cost-effectively
Difficulty: Easy

Key idea: An in-Region RDS read replica absorbs reporting queries so the primary handles only application traffic.

How to reach the answer

The slowdown comes from reporting/ML reads hitting the same primary instance.
Read scaling on RDS for PostgreSQL is done with read replicas.
A standard Multi-AZ standby cannot serve reads, so it does not help.
'MOST cost-effectively' favors a same-Region replica over cross-Region (inter-Region transfer) or DMS (extra replication instance).

Each option

AIncorrect. It offloads reads but adds inter-Region data transfer cost and latency with no requirement for another Region.
BIncorrect. A Multi-AZ DB instance standby is for failover only and cannot accept read queries.
CIncorrect. DMS requires a replication instance and a separate target database, adding cost and management for a problem native replicas solve.
DCorrect. A read replica in us-east-1 isolates the reporting load cheaply and with minimal replication latency.

Common trap: Assuming the Multi-AZ standby can be queried, which is only true for Multi-AZ DB clusters with readable standbys, not standard Multi-AZ instance deployments.

In practice: Teams routinely point BI dashboards, reporting jobs, and analytics extracts at a read replica to protect OLTP performance on the primary.

Remember: Multi-AZ is for availability, read replicas are for read scaling; keep the replica in-Region unless DR or locality requires otherwise.

Official documentation: Working with DB instance read replicas · Multi-AZ DB instance deployments

Drafted with AI assistance and checked against the answer key.

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