SAA-C03 Practice Questions: SNS Fan-Out, ElastiCache & CloudFront

Performance and decoupling questions make up a big portion of the SAA-C03 exam. These three questions cover SNS/SQS messaging patterns, database caching, and CDN delivery, all of which appear frequently.

Question 1

Every message published by a producer needs to be delivered to three separate SQS queues simultaneously. Which architecture achieves this?

• A) A single SQS Standard Queue with three consumer groups
• B) Three SQS FIFO Queues with long polling
• C) Amazon SNS topic with three SQS queue subscriptions
• D) Amazon Kinesis Data Streams with three shards

Answer: C — Amazon SNS topic with three SQS queue subscriptions

This is the classic SNS fan-out pattern. When a message is published to the SNS topic, it is delivered to all subscribers simultaneously. Each of the three SQS queues receives its own independent copy of the message, so consumers can process them at their own pace without interfering with each other.

Why the distractors are wrong:

• Single SQS queue — Each message is delivered to only one consumer. Messages are not duplicated to multiple consumers from a single queue.
• SQS FIFO queues — FIFO guarantees ordering and exactly-once processing, but doesn't replicate messages to multiple queues.
• Kinesis shards — Shards partition data across consumers; they don't replicate the same record to all consumers.

SNS fan-out diagram:

Producer
    │
    ▼
SNS Topic
  ├──► SQS Queue A  →  Consumer A (email service)
  ├──► SQS Queue B  →  Consumer B (analytics)
  └──► SQS Queue C  →  Consumer C (audit log)

On the exam: "every message must reach multiple independent services" = SNS + SQS fan-out.

Question 2

An application repeatedly reads the same rows from Amazon RDS, causing high read latency. Which service should be added to cache query results in memory?

• A) Amazon CloudFront
• B) Amazon ElastiCache
• C) Amazon DynamoDB DAX
• D) AWS Global Accelerator

Answer: B — Amazon ElastiCache

Amazon ElastiCache (Redis or Memcached) sits in front of RDS and caches the results of expensive or frequently repeated queries. Subsequent reads hit the cache instead of the database, reducing latency from milliseconds to microseconds and reducing load on RDS.

Why the distractors are wrong:

• CloudFront — A CDN for caching HTTP responses (web content, APIs) at edge locations. It doesn't integrate with RDS query results.
• DynamoDB DAX — An in-memory accelerator purpose-built for DynamoDB. It cannot cache RDS queries.
• Global Accelerator — Routes TCP/UDP traffic over the AWS backbone for improved network performance. It doesn't cache anything.

Redis vs Memcached — the exam loves this comparison:

Rule of thumb: Need durability or replication → Redis. Need maximum throughput for pure caching → Memcached.

Question 3

A global media company needs to cache and deliver video content from edge locations worldwide to minimise viewer latency. Which AWS service should they use?

• A) AWS Global Accelerator
• B) Amazon CloudFront
• C) Amazon Route 53
• D) AWS Direct Connect

Answer: B — Amazon CloudFront

Amazon CloudFront is a CDN with 400+ Points of Presence (PoPs) globally. It caches content at edge locations close to viewers, so requests are served locally rather than travelling to the origin (S3, EC2, ALB, etc.). This dramatically reduces latency for static content, video, and dynamic API responses.

Why the distractors are wrong:

• Global Accelerator — Routes TCP/UDP traffic over the AWS private backbone to the nearest AWS Region. It improves network routing without caching. Best for applications that can't be cached (e.g. real-time gaming, TCP connections).
• Route 53 — DNS service that resolves domain names to IP addresses. It does not cache or deliver content.
• Direct Connect — Dedicated private network connection between an on-premises data centre and AWS. Not relevant to content delivery.

CloudFront vs Global Accelerator — a favourite exam trap:

Key Takeaways

• "Deliver every message to multiple consumers" = SNS topic + SQS fan-out (not a single SQS queue)
• "Cache RDS query results in memory" = ElastiCache (DAX is DynamoDB-only)
• "Cache and deliver content globally" = CloudFront (Global Accelerator routes traffic but doesn't cache)