SAP-C02 Design for New Solutions Practice Question

A startup is building a serverless photo-sharing application on AWS. Users upload photos via a web app, which stores them in Amazon S3. Each upload triggers an AWS Lambda function that creates a thumbnail and stores it in another S3 bucket. The application is expected to have unpredictable traffic patterns. The startup wants to minimize costs and operational overhead while ensuring the thumbnail generation completes reliably. Which solution should a Solutions Architect recommend?

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

✓

Configure S3 event notifications to invoke a Lambda function directly upon upload to generate thumbnails.

Configuring S3 event notifications to directly invoke a Lambda function upon upload is a serverless, cost-effective solution that scales automatically with traffic, minimizes operational overhead, and ensures reliable thumbnail generation (Lambda retries on failure). Option A (ECS with Fargate) is more complex and expensive than necessary for this simple processing task. Option B (SQS queue) adds an unnecessary intermediate service, increasing latency and complexity without benefit. Option C (Auto Scaling EC2) requires managing servers, incurs costs even when idle, and is not serverless.

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 Amazon ECS with Fargate to run a container that processes S3 events and generates thumbnails.
Why it's wrong here
Using Amazon ECS with Fargate introduces unnecessary container orchestration overhead for a simple event-driven thumbnail task, whereas the requirement for minimal operational overhead and unpredictable traffic is better served by a fully managed, event-driven AWS Lambda function that scales automatically to zero when idle. This option is tempting because Fargate removes server management and can handle long-running or resource-intensive image processing workloads that exceed Lambda's 15-minute timeout or memory limits, making it correct for batch processing or high-resolution thumbnail generation.
✗
Upload to S3, send a message to an SQS queue, and have a Lambda function poll the queue to generate thumbnails.
Why it's wrong here
Adds an unnecessary intermediate service (SQS), increasing latency and complexity without benefit. Direct S3 event notification to Lambda is sufficient.
✗
Use an Auto Scaling group of EC2 instances to poll S3 for new uploads and generate thumbnails.
Why it's wrong here
Requires managing EC2 instances, which is not serverless, incurs costs even when idle, and requires scaling management.
✓
Configure S3 event notifications to invoke a Lambda function directly upon upload to generate thumbnails.
Why this is correct
Configuring S3 event notifications to directly invoke a Lambda function upon upload is a serverless, cost-effective solution that scales automatically with traffic, minimizes operational overhead, and ensures reliable thumbnail generation (Lambda retries on failure).

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

Go deeper

SAP-C02 Design for New Solutions Practice Question

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

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