- A
Amazon DAX
DAX adds an in-memory cache in front of DynamoDB to reduce read latency for repeated accesses.
- B
Amazon EFS
Why wrong: EFS is a shared file system and does not accelerate DynamoDB read operations.
- C
AWS Lambda
Why wrong: Lambda is a compute service and does not provide caching for DynamoDB reads.
- D
Amazon SNS
Why wrong: SNS is used for pub/sub messaging and does not reduce latency for repeated database reads.
Question 1,039 of 1,040
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure 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 mobile app reads the same product details many times per minute from Amazon DynamoDB. The table design is already correct, but repeated reads are still causing noticeable latency. Which service should the team add to improve read performance?
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
✓
Amazon DAX
Amazon DAX (DynamoDB Accelerator) is an in-memory cache specifically designed for DynamoDB. It reduces read latency from single-digit milliseconds to microseconds by caching frequently accessed items, which directly addresses the repeated read pattern described in the question.
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.
- ✓
Amazon DAX
Why this is correct
DAX adds an in-memory cache in front of DynamoDB to reduce read latency for repeated accesses.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon EFS
Why it's wrong here
EFS is a shared file system and does not accelerate DynamoDB read operations.
When this WOULD be correct
A question where an application running on multiple EC2 instances needs a shared, scalable file system for storing and accessing common files (e.g., configuration files, logs, or media) across instances. EFS would be the correct choice for a shared NFS file system.
- ✗
AWS Lambda
Why it's wrong here
Lambda is a compute service and does not provide caching for DynamoDB reads.
When this WOULD be correct
A question where a DynamoDB stream triggers a function to transform or aggregate data before storing it elsewhere (e.g., update an Amazon ElastiCache cluster or write to Amazon S3) would make Lambda the correct answer. For example: 'A team needs to process item changes from a DynamoDB table and update a materialized view in near real time.'
- ✗
Amazon SNS
Why it's wrong here
SNS is used for pub/sub messaging and does not reduce latency for repeated database reads.
When this WOULD be correct
A correct scenario: 'An application needs to send real-time alerts to multiple subscribers (e.g., email, SMS, Lambda) whenever a new item is inserted into a DynamoDB table.' In that case, Amazon SNS would be the right service to fan out notifications.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Amazon DAXCorrect answer▾
Why this is correct
DAX adds an in-memory cache in front of DynamoDB to reduce read latency for repeated accesses.
✗Amazon EFSWrong answer — click to see why▾
Why this is wrong here
Amazon EFS is a file storage service for EC2 instances, not a caching layer for DynamoDB. It cannot reduce read latency for DynamoDB queries because it does not integrate with DynamoDB's API or provide in-memory acceleration.
★ When this WOULD be the correct answer
A question where an application running on multiple EC2 instances needs a shared, scalable file system for storing and accessing common files (e.g., configuration files, logs, or media) across instances. EFS would be the correct choice for a shared NFS file system.
Why candidates choose this
Candidates might confuse EFS as a general-purpose 'cache' because it offers low-latency file access, but they overlook that it is not designed for database query caching and cannot be used with DynamoDB directly.
✗AWS LambdaWrong answer — click to see why▾
Why this is wrong here
AWS Lambda is a compute service for running code in response to events, not a caching layer. It cannot reduce read latency for repeated DynamoDB reads because it does not cache data; adding Lambda would introduce additional invocation overhead, worsening latency.
★ When this WOULD be the correct answer
A question where a DynamoDB stream triggers a function to transform or aggregate data before storing it elsewhere (e.g., update an Amazon ElastiCache cluster or write to Amazon S3) would make Lambda the correct answer. For example: 'A team needs to process item changes from a DynamoDB table and update a materialized view in near real time.'
Why candidates choose this
Candidates may think Lambda can 'speed up' reads by preprocessing or caching data, but Lambda is stateless and not designed for low-latency data retrieval. The temptation comes from overgeneralizing Lambda's role in optimizing data pipelines.
✗Amazon SNSWrong answer — click to see why▾
Why this is wrong here
Amazon SNS is a pub/sub messaging service for notifications and event-driven workflows, not a caching layer. It cannot reduce read latency for repeated DynamoDB reads because it does not store or serve data from a cache.
★ When this WOULD be the correct answer
A correct scenario: 'An application needs to send real-time alerts to multiple subscribers (e.g., email, SMS, Lambda) whenever a new item is inserted into a DynamoDB table.' In that case, Amazon SNS would be the right service to fan out notifications.
Why candidates choose this
Candidates might think SNS can cache or buffer repeated reads because it's a managed service that can decouple components, but they confuse its notification role with caching or data serving capabilities.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse DAX with ElastiCache (which is generic and not DynamoDB-native) or assume that Lambda or SNS can somehow accelerate reads, but DAX is the only service purpose-built for DynamoDB read acceleration.
Detailed technical explanation
How to think about this question
DAX maintains a write-through cache that synchronizes with DynamoDB, so reads for cached items bypass the DynamoDB storage engine entirely. Under the hood, DAX uses a cluster of nodes with in-memory caches that support item-level and query/scan caching, and it automatically invalidates stale data based on TTL or write operations. In a real-world scenario, a mobile app fetching product details thousands of times per minute would see latency drop from ~5 ms to under 1 ms with DAX, while also reducing DynamoDB read capacity unit consumption.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon DAX — Amazon DAX (DynamoDB Accelerator) is an in-memory cache specifically designed for DynamoDB. It reduces read latency from single-digit milliseconds to microseconds by caching frequently accessed items, which directly addresses the repeated read pattern described in the question.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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