CLF-C02 Cloud Technology and Services Practice Question
A company has a mobile application that allows users to upload profile photos. When a new photo is uploaded to an Amazon S3 bucket, the application must automatically create a thumbnail version and store it in another S3 bucket. The company wants a solution that runs only when needed, scales automatically, and requires no management of underlying servers. Which AWS service should the company use to meet these requirements?
⚠ Common exam trap
Many exam-takers confuse AWS Batch with event-driven processing, but Batch is optimized for scheduled or queued batch jobs, not for real-time, per-object triggers like S3 uploads.
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 events, such as an S3 PUT object event. It automatically scales from zero to thousands of concurrent executions based on the number of incoming uploads, and requires no server management, perfectly meeting the requirement for an on-demand, auto-scaling thumbnail generation solution.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
AWS Lambda
Why this is correct
AWS Lambda is the correct choice because it is a serverless compute service that can be triggered directly by Amazon S3 object-created events. When a user uploads a profile photo, Lambda executes the thumbnail-generation code automatically, scales horizontally to handle concurrent uploads without any infrastructure provisioning, and incurs cost only for the compute time actually consumed during the invocation.
- ✗
AWS Batch
Why it's wrong here
AWS Batch is designed for running large-scale batch computing jobs, not for event-driven image processing. It fails because the requirement demands automatic thumbnail creation triggered by an S3 upload, which AWS Batch cannot natively initiate without additional orchestration. It is tempting because Batch does handle serverless compute for scheduled or queued workloads, but it would be correct only for processing jobs that run on a defined schedule or when tasks are submitted to a job queue, not for real-time object creation events.
When this WOULD be correct
A company needs to run a large-scale, compute-intensive batch job (e.g., video transcoding or genomic analysis) that can be split into multiple parallel tasks, and they want to manage job dependencies and retries. AWS Batch would be the correct answer because it orchestrates batch workloads across EC2 or Fargate with automatic scaling.
- ✗
Amazon EC2
Why it's wrong here
Amazon EC2 is incorrect because it requires you to provision and manage virtual servers that run continuously, leading to idle resource costs when no uploads are occurring. EC2 is not natively event-driven; to trigger thumbnail creation on an S3 upload you would need additional components such as Lambda or EventBridge, and you would still be responsible for patching, scaling, and maintaining the instances, contradicting the serverless, low-management requirement.
When this WOULD be correct
If the question required a long-running application with custom OS configurations, persistent storage, or specific software installations that cannot be containerized or run in a serverless function, Amazon EC2 would be the correct choice.
- ✗
Amazon ECS with EC2 launch type
Why it's wrong here
Amazon ECS with the EC2 launch type requires managing a cluster of EC2 instances. While it can run containers, it is not serverless and does not automatically trigger based on S3 events without additional components like Lambda or EventBridge.
When this WOULD be correct
A company needs to run containerized batch processing jobs that require persistent storage or GPU resources, and is willing to manage EC2 instances for cost optimization or compliance reasons.
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 the correct choice because it is a serverless compute service that can be triggered directly by Amazon S3 object-created events. When a user uploads a profile photo, Lambda executes the thumbnail-generation code automatically, scales horizontally to handle concurrent uploads without any infrastructure provisioning, and incurs cost only for the compute time actually consumed during the invocation.
✗AWS BatchWrong answer — click to see why▾
Why this is wrong here
AWS Batch is designed for batch computing jobs that require orchestration of compute resources, not for event-driven, short-lived tasks like image processing triggered by S3 uploads. It does not natively integrate with S3 events to trigger jobs automatically without additional setup.
★ When this WOULD be the correct answer
A company needs to run a large-scale, compute-intensive batch job (e.g., video transcoding or genomic analysis) that can be split into multiple parallel tasks, and they want to manage job dependencies and retries. AWS Batch would be the correct answer because it orchestrates batch workloads across EC2 or Fargate with automatic scaling.
Why candidates choose this
Candidates might think 'batch processing' applies to any automated processing task, including thumbnail generation, and overlook that AWS Lambda is simpler and more appropriate for event-driven, short-duration tasks.
✗Amazon EC2Wrong answer — click to see why▾
Why this is wrong here
Amazon EC2 requires manual management of underlying servers and does not automatically scale based on S3 events. It would need constant running instances or complex auto-scaling setups, violating the 'runs only when needed' and 'no management' requirements.
★ When this WOULD be the correct answer
If the question required a long-running application with custom OS configurations, persistent storage, or specific software installations that cannot be containerized or run in a serverless function, Amazon EC2 would be the correct choice.
Why candidates choose this
Candidates may think EC2 is the default compute service for any workload, overlooking the serverless and event-driven nature of the requirement. They might not realize that Lambda can directly respond to S3 events without provisioning servers.
✗Amazon ECS with EC2 launch typeWrong answer — click to see why▾
Why this is wrong here
Amazon ECS with EC2 launch type requires managing EC2 instances, which does not meet the requirement of no server management. It also does not automatically trigger on S3 uploads without additional setup like EventBridge.
★ When this WOULD be the correct answer
A company needs to run containerized batch processing jobs that require persistent storage or GPU resources, and is willing to manage EC2 instances for cost optimization or compliance reasons.
Why candidates choose this
Candidates may think ECS is serverless, but the EC2 launch type involves managing servers, confusing it with Fargate. They might also assume containers are needed for image processing.
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?”
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
Related to this question
About these practice questions
One of 988 original CLF-C02 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on CLF-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company runs a web application that allows users to upload images. After each upload, the application must perform several background processing tasks (e.g., resizing, generating thumbnails) that take up to 30 seconds each. Users should receive an immediate response and the processing should continue asynchronously. The company wants a solution that scales automatically with the number of uploads and requires no server management. Which AWS service should the company use to run these background processing tasks?
medium- ✓ A.AWS Lambda
- B.Amazon EC2 with Auto Scaling
- C.Amazon ECS with AWS Fargate
- D.AWS Batch
Why A: AWS Lambda is the correct choice because it is a serverless compute service that executes code in response to events, such as an image upload to Amazon S3. It scales automatically with the number of uploads, requires no server management, and can run background tasks like resizing and thumbnail generation within its 15-minute maximum execution time, easily accommodating the 30-second processing requirement. Users receive an immediate response because the upload triggers Lambda asynchronously, decoupling the frontend from the processing.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.