Question 727 of 988
CLF-C02 Cloud Technology and Services Practice Question
A company is developing a REST API that processes customer orders. The API receives JSON payloads via HTTPS and performs short-lived operations, such as data validation, transformation, and writing to a database. The workload is very unpredictable: sometimes there are long periods of inactivity, but during flash sales the API may receive thousands of requests per second for a few minutes. The company wants a fully managed compute service that automatically scales to handle any request volume, charges only for the compute time used during execution, and requires no server provisioning or ongoing infrastructure management. Which AWS service should the company use?
⚠ Common exam trap
Test-takers frequently confuse 'fully managed' with 'container orchestration' and select ECS with Fargate, overlooking that Lambda is the only option that charges strictly per execution (not per provisioned resource) and automatically scales to zero during inactivity without any ongoing cost.
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 fully managed, event-driven compute service that automatically scales from zero to thousands of concurrent executions in response to incoming HTTPS requests. It charges only for the compute time consumed during execution (in 1ms increments), requires no server provisioning, and is ideal for short-lived operations like data validation, transformation, and database writes. The unpredictable, bursty workload pattern—long idle periods followed by flash sales—maps perfectly to Lambda's pay-per-use model and automatic scaling.
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 with Auto Scaling
Why it's wrong here
Amazon EC2 with Auto Scaling requires provisioning and managing virtual servers. Scaling is based on metrics like CPU utilization, not per individual request. Even when idle, running instances incur charges. This does not meet the need for fully managed, per-request scaling and pay-per-use billing.
When this WOULD be correct
A company needs to run a long-lived application (e.g., a web server) that requires full control over the operating system, software installations, and persistent storage. The workload is predictable and requires consistent performance, and the company is willing to manage scaling policies and instance lifecycle.
- ✓
AWS Lambda
Why this is correct
AWS Lambda is a serverless compute service that executes code in response to events. It automatically scales to handle any volume of requests, charging only for the compute time consumed during execution (per millisecond). No servers to provision or manage, making it ideal for unpredictable, short-lived workloads.
- ✗
Amazon ECS with Fargate launch type
Why it's wrong here
Amazon ECS with Fargate eliminates server management but still requires provisioning and scaling of task definitions and cluster capacity, meaning it does not offer the automatic, sub-second scaling to zero during inactivity that a serverless function provides. It is tempting because Fargate is fully managed and charges per second, making it suitable for containerised microservices with steady or predictable throughput, but it cannot match the instantaneous, request-level scaling of a Lambda-based architecture for unpredictable, short-lived API workloads.
When this WOULD be correct
A company needs to run containerized applications that require persistent background processes, long-running jobs (over 15 minutes), or specific container configurations (e.g., custom networking, GPU support). The workload is steady or predictable, and the company prefers to manage containers without provisioning servers.
- ✗
Amazon Lightsail
Why it's wrong here
Amazon Lightsail offers preconfigured virtual private servers at a fixed monthly price. It does not automatically scale with request volume, and billing is not based on actual compute time used. It is not suitable for a highly variable, pay-per-use workload.
When this WOULD be correct
A company needs a simple, predictable-cost virtual private server for a small web application with steady traffic, and wants to avoid managing EC2 instances directly. The workload does not require automatic scaling or a pay-per-execution model.
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 executes code in response to events. It automatically scales to handle any volume of requests, charging only for the compute time consumed during execution (per millisecond). No servers to provision or manage, making it ideal for unpredictable, short-lived workloads.
✗Amazon EC2 with Auto ScalingWrong answer — click to see why▾
Why this is wrong here
EC2 with Auto Scaling requires provisioning and managing EC2 instances, even with Auto Scaling. It does not charge only for compute time used during execution (you pay for running instances even when idle) and requires ongoing infrastructure management, contradicting the fully managed, pay-per-execution requirements.
★ When this WOULD be the correct answer
A company needs to run a long-lived application (e.g., a web server) that requires full control over the operating system, software installations, and persistent storage. The workload is predictable and requires consistent performance, and the company is willing to manage scaling policies and instance lifecycle.
Why candidates choose this
Candidates may think Auto Scaling provides automatic scaling and is serverless-like, but they overlook that EC2 still requires server management and charges for idle time, not just execution time.
✗Amazon ECS with Fargate launch typeWrong answer — click to see why▾
Why this is wrong here
Amazon ECS with Fargate still requires managing task definitions, container images, and cluster scaling policies, and it charges for provisioned resources (vCPU and memory) even when idle, not just for execution time. The question demands a fully managed service that charges only for compute time during execution, which AWS Lambda meets with its per-request billing.
★ When this WOULD be the correct answer
A company needs to run containerized applications that require persistent background processes, long-running jobs (over 15 minutes), or specific container configurations (e.g., custom networking, GPU support). The workload is steady or predictable, and the company prefers to manage containers without provisioning servers.
Why candidates choose this
Candidates may confuse Fargate's 'serverless containers' with Lambda's 'serverless functions,' overlooking that Fargate still incurs costs for idle resources and requires more configuration, while Lambda is truly pay-per-execution and simpler for short-lived, event-driven tasks.
✗Amazon LightsailWrong answer — click to see why▾
Why this is wrong here
Amazon Lightsail is a simplified VPS service that requires manual scaling and does not automatically scale to handle thousands of requests per second during flash sales. It also charges for fixed monthly pricing, not just for compute time used during execution.
★ When this WOULD be the correct answer
A company needs a simple, predictable-cost virtual private server for a small web application with steady traffic, and wants to avoid managing EC2 instances directly. The workload does not require automatic scaling or a pay-per-execution model.
Why candidates choose this
Candidates may choose Lightsail because it is marketed as a simple, fully managed service, but they overlook its lack of automatic scaling and pay-per-execution billing, which are key requirements in this question.
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
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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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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