- A
Amazon EC2 Auto Scaling group
Why wrong: EC2 Auto Scaling helps manage instance capacity but requires running servers even when idle; it is not natively triggered by S3 events without additional setup and does not offer pay-per-execution billing.
- B
AWS Lambda
AWS Lambda is a serverless compute service that can be triggered directly by S3 events. It runs code only when invoked, scales automatically, and bills only for the compute time used, meeting all the stated requirements.
- C
Amazon ECS with Fargate
Why wrong: Amazon ECS with Fargate runs containers without managing servers, but it is not designed for event-driven invocation in the same way as Lambda. Typically, an intermediary service (like Lambda) would be needed to trigger a container task, and you pay for running containers even while waiting for work.
- D
Amazon Elastic Beanstalk
Why wrong: Elastic Beanstalk is a PaaS service that automates deployment and scaling of applications, but it requires running environments (EC2 instances) that incur costs even when idle. It is not an event-driven compute service and does not provide pay-per-execution billing.
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 development team is building a serverless application that processes image uploads to Amazon S3. The application needs to automatically generate a thumbnail version of each uploaded image and store it in a separate S3 bucket. The team wants to minimize operational overhead and only pay for the compute time used during thumbnail generation. Which AWS service should the team use to execute the thumbnail generation code in response to S3 upload events?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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 can be triggered directly by S3 events (e.g., s3:ObjectCreated:*). This allows the thumbnail generation code to run automatically in response to each image upload, with no servers to manage and billing based only on the compute time consumed during execution.
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 EC2 Auto Scaling group
Why it's wrong here
EC2 Auto Scaling helps manage instance capacity but requires running servers even when idle; it is not natively triggered by S3 events without additional setup and does not offer pay-per-execution billing.
- ✓
AWS Lambda
Why this is correct
AWS Lambda is a serverless compute service that can be triggered directly by S3 events. It runs code only when invoked, scales automatically, and bills only for the compute time used, meeting all the stated requirements.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon ECS with Fargate
Why it's wrong here
Amazon ECS with Fargate runs containers without managing servers, but it is not designed for event-driven invocation in the same way as Lambda. Typically, an intermediary service (like Lambda) would be needed to trigger a container task, and you pay for running containers even while waiting for work.
- ✗
Amazon Elastic Beanstalk
Why it's wrong here
Elastic Beanstalk is a PaaS service that automates deployment and scaling of applications, but it requires running environments (EC2 instances) that incur costs even when idle. It is not an event-driven compute service and does not provide pay-per-execution billing.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse 'serverless' with container services like Fargate, but Lambda is the only option that natively integrates with S3 events and charges only for execution time, while Fargate still requires managing task definitions and incurs costs for running containers even when idle.
Detailed technical explanation
How to think about this question
Under the hood, S3 can publish event notifications directly to a Lambda function via a resource-based policy, invoking the function synchronously with the event payload containing bucket name, object key, and size. Lambda then spins up an execution environment (e.g., a microVM) within milliseconds, runs the thumbnail generation code (e.g., using Pillow or Sharp), and writes the result to the destination bucket — all within the function's maximum 15-minute timeout. A real-world scenario where this matters is high-volume image processing pipelines, where Lambda's concurrency scaling (up to 1,000 concurrent executions by default) handles thousands of uploads per second without provisioning.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
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 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 can be triggered directly by S3 events (e.g., s3:ObjectCreated:*). This allows the thumbnail generation code to run automatically in response to each image upload, with no servers to manage and billing based only on the compute time consumed during execution.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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 →
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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