- A
Run the thumbnailing code on Amazon EC2 instances behind an Application Load Balancer
Why wrong: While EC2 instances can execute code, this approach requires manual scaling configuration, ongoing instance management, and a load balancer. It does not automatically react to S3 uploads without additional integration (e.g., S3 event notifications to an Amazon SQS queue that an EC2 instance polls). This adds operational overhead and does not provide the desired serverless, event-driven capability.
- B
AWS Lambda
AWS Lambda is a serverless function-as-a-service (FaaS) platform that runs code in response to events and automatically manages the underlying compute resources. It can be directly triggered by S3 bucket notifications (e.g., s3:ObjectCreated events). Lambda scales instantly to handle the upload volume and requires no server provisioning, making it ideal for this workload.
- C
Amazon ECS with AWS Fargate launch type
Why wrong: Amazon ECS with Fargate is a serverless container orchestrator, but it requires building container images, defining task definitions, and managing a cluster. For a simple image resizing task that is event-driven and short-lived, using containers introduces unnecessary complexity compared to Lambda. Lambda is more suited for this granular, event-triggered workload.
- D
AWS Elastic Beanstalk
Why wrong: AWS Elastic Beanstalk is a Platform as a Service (PaaS) that automates the deployment and scaling of web applications. It still provisions underlying EC2 instances and manages the environment. It is not natively event-driven by S3 object creation; it expects a web server to handle HTTP requests. Using it for automated thumbnail generation upon S3 uploads would require additional architectural components and is not as straightforward as a Lambda trigger.
CLF-C02 Cloud Technology and Services Practice Question
This CLF-C02 practice question tests your understanding of cloud technology and services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 media company processes user-uploaded images. When a user uploads a high-resolution image to an Amazon S3 bucket, the company must automatically generate three resized thumbnail versions (small, medium, large) within seconds. The company wants a solution that requires no infrastructure management and scales automatically to handle thousands of concurrent uploads. Which AWS service should the company use to execute the thumbnail generation code?
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
AWS Lambda
AWS Lambda is the correct choice because it is a serverless compute service that executes code in response to S3 events (e.g., object creation) without provisioning or managing servers. It scales automatically to handle thousands of concurrent uploads, and the 15-minute execution timeout is sufficient for generating three thumbnail versions within seconds. This meets the requirement for no infrastructure management and automatic scaling.
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.
- ✗
Run the thumbnailing code on Amazon EC2 instances behind an Application Load Balancer
Why it's wrong here
While EC2 instances can execute code, this approach requires manual scaling configuration, ongoing instance management, and a load balancer. It does not automatically react to S3 uploads without additional integration (e.g., S3 event notifications to an Amazon SQS queue that an EC2 instance polls). This adds operational overhead and does not provide the desired serverless, event-driven capability.
- ✓
AWS Lambda
Why this is correct
AWS Lambda is a serverless function-as-a-service (FaaS) platform that runs code in response to events and automatically manages the underlying compute resources. It can be directly triggered by S3 bucket notifications (e.g., s3:ObjectCreated events). Lambda scales instantly to handle the upload volume and requires no server provisioning, making it ideal for this workload.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon ECS with AWS Fargate launch type
Why it's wrong here
Amazon ECS with Fargate is a serverless container orchestrator, but it requires building container images, defining task definitions, and managing a cluster. For a simple image resizing task that is event-driven and short-lived, using containers introduces unnecessary complexity compared to Lambda. Lambda is more suited for this granular, event-triggered workload.
- ✗
AWS Elastic Beanstalk
Why it's wrong here
AWS Elastic Beanstalk is a Platform as a Service (PaaS) that automates the deployment and scaling of web applications. It still provisions underlying EC2 instances and manages the environment. It is not natively event-driven by S3 object creation; it expects a web server to handle HTTP requests. Using it for automated thumbnail generation upon S3 uploads would require additional architectural components and is not as straightforward as a Lambda trigger.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may choose Amazon ECS with Fargate (Option C) thinking it is the only serverless container option, but they overlook that Lambda is purpose-built for short-lived, event-driven tasks like image processing and requires no cluster or task definition management, making it the simpler and more cost-effective choice for this use case.
Detailed technical explanation
How to think about this question
AWS Lambda integrates natively with S3 via event notifications, allowing the function to be invoked synchronously or asynchronously with the S3 object key and bucket name passed in the event payload. The function can use the AWS SDK to download the original image, generate thumbnails using libraries like Pillow or Sharp, and upload them back to a separate S3 prefix or bucket. Lambda's concurrency limit (default 1,000 per region) can be increased via a support request to handle spikes, and its ephemeral storage (/tmp) of 512 MB to 10 GB is sufficient for image processing.
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.
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Cloud Technology and Services — This question tests Cloud Technology and Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: AWS Lambda — AWS Lambda is the correct choice because it is a serverless compute service that executes code in response to S3 events (e.g., object creation) without provisioning or managing servers. It scales automatically to handle thousands of concurrent uploads, and the 15-minute execution timeout is sufficient for generating three thumbnail versions within seconds. This meets the requirement for no infrastructure management and automatic scaling.
What should I do if I get this CLF-C02 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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Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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Last reviewed: Jun 11, 2026
This CLF-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CLF-C02 exam.
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