- A
Amazon EC2 Auto Scaling group
Why wrong: An Auto Scaling group manages a fleet of EC2 instances, which require provisioning and ongoing management. It is not event-driven and would need additional services to respond to S3 uploads, increasing complexity and cost.
- B
AWS Lambda
AWS Lambda is a serverless compute service that can be triggered directly by Amazon S3 events. It runs code only when an image is uploaded, scales automatically, and bills per millisecond of execution. This matches the requirements for minimal overhead and pay-per-use.
- C
Amazon ECS with Fargate
Why wrong: Amazon ECS with Fargate runs containerized applications without managing servers, but it is typically used for long-running or scheduled tasks. To trigger it from S3 events, you would need an intermediary service like Amazon EventBridge or a custom polling mechanism, adding complexity and potential cost.
- D
AWS Batch
Why wrong: AWS Batch is a fully managed batch computing service for running large-scale batch jobs. It is not designed for real-time event-driven processing and would require orchestration to run on each S3 upload, leading to unnecessary overhead and latency.
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 company wants to build a serverless application that processes images uploaded to an Amazon S3 bucket. When a user uploads a new image, the application must automatically resize the image to multiple dimensions and store the resized versions in the same bucket under a different prefix. The company wants to minimize operational overhead and pay only for the compute time used. Which AWS service should be used to run the image processing code?
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 runs code in response to S3 events, such as object creation. It automatically scales with the number of uploads, charges only for the compute time consumed (per 100ms increments), and requires no infrastructure management, making it ideal for event-driven image processing tasks.
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
An Auto Scaling group manages a fleet of EC2 instances, which require provisioning and ongoing management. It is not event-driven and would need additional services to respond to S3 uploads, increasing complexity and cost.
When this WOULD be correct
A company needs to run a long-running, stateful image processing application that requires persistent storage, custom operating system configurations, or specific GPU instances for machine learning tasks, and is willing to manage the underlying infrastructure.
- ✓
AWS Lambda
Why this is correct
AWS Lambda is a serverless compute service that can be triggered directly by Amazon S3 events. It runs code only when an image is uploaded, scales automatically, and bills per millisecond of execution. This matches the requirements for minimal overhead and pay-per-use.
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 containerized applications without managing servers, but it is typically used for long-running or scheduled tasks. To trigger it from S3 events, you would need an intermediary service like Amazon EventBridge or a custom polling mechanism, adding complexity and potential cost.
When this WOULD be correct
A company needs to run a long-running image processing task (e.g., >15 minutes) that requires custom libraries or specific runtime environments not supported by Lambda, and wants to avoid managing servers. ECS with Fargate would be correct for containerized workloads with flexible scaling.
- ✗
AWS Batch
Why it's wrong here
AWS Batch is a fully managed batch computing service for running large-scale batch jobs. It is not designed for real-time event-driven processing and would require orchestration to run on each S3 upload, leading to unnecessary overhead and latency.
When this WOULD be correct
A company needs to run a long-running, compute-intensive image processing job (e.g., applying complex filters to thousands of images) that can be queued and executed as a batch job. The job requires access to GPU instances and can tolerate startup delays, making AWS Batch the right choice.
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 CLF-C02 exam frequently reuses these exact scenarios with slightly different constraints.
✓AWS LambdaCorrect answer▾
Why this is correct
AWS Lambda is a serverless compute service that can be triggered directly by Amazon S3 events. It runs code only when an image is uploaded, scales automatically, and bills per millisecond of execution. This matches the requirements for minimal overhead and pay-per-use.
✗Amazon EC2 Auto Scaling groupWrong answer — click to see why▾
Why this is wrong here
Amazon EC2 Auto Scaling groups require managing virtual servers, patching, and scaling policies, which increases operational overhead. The question specifies a serverless application that minimizes overhead and pays only for compute time used, which EC2 does not provide.
★ When this WOULD be the correct answer
A company needs to run a long-running, stateful image processing application that requires persistent storage, custom operating system configurations, or specific GPU instances for machine learning tasks, and is willing to manage the underlying infrastructure.
Why candidates choose this
Candidates may think EC2 Auto Scaling is suitable for any scalable workload, but they overlook the serverless requirement and the operational overhead of managing EC2 instances.
✗Amazon ECS with FargateWrong answer — click to see why▾
Why this is wrong here
Amazon ECS with Fargate is not serverless in the sense of pay-per-invocation; it requires running containers continuously or on a schedule, incurring costs even when idle, and adds operational overhead for container management compared to AWS Lambda's event-driven, zero-administration model.
★ When this WOULD be the correct answer
A company needs to run a long-running image processing task (e.g., >15 minutes) that requires custom libraries or specific runtime environments not supported by Lambda, and wants to avoid managing servers. ECS with Fargate would be correct for containerized workloads with flexible scaling.
Why candidates choose this
Candidates may think Fargate is serverless and suitable for event-driven tasks, but they overlook Lambda's simpler integration with S3 events and its true pay-per-use model for short-lived functions.
✗AWS BatchWrong answer — click to see why▾
Why this is wrong here
AWS Batch is designed for batch computing jobs that run on a managed cluster, not for event-driven, short-lived functions triggered by S3 uploads. It incurs provisioning overhead and is not ideal for lightweight image resizing tasks that require minimal compute time per invocation.
★ When this WOULD be the correct answer
A company needs to run a long-running, compute-intensive image processing job (e.g., applying complex filters to thousands of images) that can be queued and executed as a batch job. The job requires access to GPU instances and can tolerate startup delays, making AWS Batch the right choice.
Why candidates choose this
Candidates may think 'batch processing' fits image resizing because resizing multiple dimensions sounds like a batch job, but they overlook the event-driven, real-time nature of the requirement and the operational simplicity of Lambda.
Analysis generated from the official CLF-C02blueprint 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 choose Amazon ECS with Fargate because they think 'serverless containers' are always the best option, but they overlook that Lambda is simpler, cheaper, and more appropriate for lightweight, event-driven tasks like image resizing, whereas Fargate adds unnecessary overhead for container orchestration.
Detailed technical explanation
How to think about this question
Under the hood, AWS Lambda integrates with S3 via event notifications using the PUT Object API; when an image is uploaded, S3 publishes an event to Lambda, which invokes the function with the object key and bucket name. The function can use the AWS SDK to download the original image, resize it using libraries like Pillow (Python) or Sharp (Node.js), and upload the resized versions back to S3 under a different prefix—all within the 15-minute execution timeout and 512 MB to 10 GB memory range. A real-world scenario is a photo-sharing app where users upload high-resolution images; Lambda resizes them to thumbnails, medium, and large versions, and the cost is minimal because Lambda only runs when a new image is uploaded.
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.
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 |
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 runs code in response to S3 events, such as object creation. It automatically scales with the number of uploads, charges only for the compute time consumed (per 100ms increments), and requires no infrastructure management, making it ideal for event-driven image processing tasks.
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.
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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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