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Question 166 of 1,040

Design High-Performing Architectures →easyMultiple ChoiceObjective-mapped

Quick Answer

The answer is to add read replicas to an RDS or Aurora cluster while keeping the primary instance for writes. This design choice directly improves read performance for a relational database under a read-heavy workload because it offloads complex queries—such as joins and aggregations—from the primary database to dedicated replicas, preserving full SQL capabilities and the relational data model. On the SAA-C03 exam, this scenario tests your understanding of scaling read traffic without sacrificing relational features; a common trap is to suggest caching layers like ElastiCache, which cannot handle complex joins, or sharding, which breaks the relational model. Remember that read replicas maintain ACID compliance and can be promoted to primaries for high availability, but they are not for disaster recovery across regions unless using Aurora Global Database. Memory tip: “Read replicas for reads, primary for writes—keep your joins and aggregations on the copies.”

SAA-C03 Design High-Performing Architectures Practice Question

This SAA-C03 practice question tests your understanding of design high-performing architectures. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

A customer-facing application has a relational data model and needs frequent complex queries (joins and aggregations), but it also experiences a significant read-heavy workload. Which design choice best improves read performance while keeping relational features?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

Question 1easymultiple choice

Full question →

A
Use DynamoDB with a single partition key and avoid indexes to keep writes simple.
Why wrong: DynamoDB is great for key-value and document patterns, but complex joins/aggregations require redesign. Avoiding indexes would likely hurt query flexibility and performance. This option conflicts with the relational query requirement.
B
Add read replicas to an RDS or Aurora cluster and keep the primary for writes.
Read replicas offload read operations from the primary database instance, improving read throughput and reducing contention with writes. RDS/Aurora preserve relational capabilities like joins and SQL queries. This is a common and practical way to scale performance for read-heavy workloads without completely changing the data model.
C
Store the data in S3 and query it directly from the application without a database.
Why wrong: S3 is object storage and is not designed for low-latency relational query workloads. Querying directly would be slow and operationally complex. Complex joins/aggregations would not be straightforward.
D
Switch the database to DynamoDB but keep using the same relational SQL queries and joins.
Why wrong: DynamoDB does not support SQL joins in the same way relational databases do. Moving to DynamoDB generally requires a query-pattern redesign with keys and indexes. Keeping the same query approach would not work as intended.

Full breakdown with real-world context →

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

✓

Add read replicas to an RDS or Aurora cluster and keep the primary for writes.

Adding read replicas to an RDS or Aurora cluster offloads read traffic from the primary instance, improving read performance for complex queries (joins and aggregations) while preserving the full relational data model and SQL capabilities. Aurora’s distributed storage layer also allows replicas to serve reads with minimal replication lag, making this the optimal choice for read-heavy workloads that require relational features.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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 DynamoDB with a single partition key and avoid indexes to keep writes simple.
Why it's wrong here
DynamoDB is great for key-value and document patterns, but complex joins/aggregations require redesign. Avoiding indexes would likely hurt query flexibility and performance. This option conflicts with the relational query requirement.
✓
Add read replicas to an RDS or Aurora cluster and keep the primary for writes.
Why this is correct
Read replicas offload read operations from the primary database instance, improving read throughput and reducing contention with writes. RDS/Aurora preserve relational capabilities like joins and SQL queries. This is a common and practical way to scale performance for read-heavy workloads without completely changing the data model.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Store the data in S3 and query it directly from the application without a database.
Why it's wrong here
S3 is object storage and is not designed for low-latency relational query workloads. Querying directly would be slow and operationally complex. Complex joins/aggregations would not be straightforward.
✗
Switch the database to DynamoDB but keep using the same relational SQL queries and joins.
Why it's wrong here
DynamoDB does not support SQL joins in the same way relational databases do. Moving to DynamoDB generally requires a query-pattern redesign with keys and indexes. Keeping the same query approach would not work as intended.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume NoSQL (DynamoDB) is always the best choice for read-heavy workloads, overlooking that complex relational queries and joins are not supported, making read replicas on RDS/Aurora the correct relational scaling solution.

Detailed technical explanation

How to think about this question

Aurora read replicas share the same underlying storage volume as the primary, so replication lag is typically sub-100ms and replicas can serve read traffic without additional storage overhead. For RDS, read replicas use MySQL or PostgreSQL native asynchronous replication, and you can promote a replica to a primary in case of failure, providing both read scaling and high availability. In practice, read-heavy applications like reporting dashboards or customer-facing analytics benefit by routing SELECT queries to replicas while keeping writes on the primary, avoiding contention on the same instance.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

TExam Day Tips

Watch for words such as best, first, most likely and least administrative effort.
Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this SAA-C03 question test?

Design High-Performing Architectures — This question tests Design High-Performing Architectures — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Add read replicas to an RDS or Aurora cluster and keep the primary for writes. — Adding read replicas to an RDS or Aurora cluster offloads read traffic from the primary instance, improving read performance for complex queries (joins and aggregations) while preserving the full relational data model and SQL capabilities. Aurora’s distributed storage layer also allows replicas to serve reads with minimal replication lag, making this the optimal choice for read-heavy workloads that require relational features.

What should I do if I get this SAA-C03 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Same concept, more angles

1 more ways this is tested on SAA-C03

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 customer-facing application has a relational data model and needs frequent complex queries (joins and aggregations), but it also experiences a significant read-heavy workload. Which design choice best improves read performance while keeping relational features?

easy

A.Use DynamoDB with a single partition key and avoid indexes to keep writes simple.
✓ B.Add read replicas to an RDS or Aurora cluster and keep the primary for writes.
C.Store the data in S3 and query it directly from the application without a database.
D.Switch the database to DynamoDB but keep using the same relational SQL queries and joins.

Why B: Adding read replicas to an RDS or Aurora cluster offloads read traffic from the primary instance, improving read performance for complex queries (joins and aggregations) while preserving the relational data model. Aurora automatically scales read replicas and uses a shared storage volume, making this highly efficient for read-heavy workloads.

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