CLF-C02 Cloud Technology and Services Practice Question
A company's application experiences traffic spikes every weekday morning when employees arrive at work. During off-hours, very few users are active. Which AWS feature automatically adjusts the number of EC2 instances based on demand, adding instances during peak hours and removing them during quiet periods?
⚠ Common exam trap
Many candidates confuse Elastic Load Balancing with Auto Scaling, assuming load balancers automatically scale instances, when in fact ELB only distributes traffic and requires Auto Scaling to adjust capacity.
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
✓
Amazon EC2 Auto Scaling
Amazon EC2 Auto Scaling is the correct service because it automatically adjusts the number of EC2 instances in response to demand, using scaling policies (e.g., scheduled scaling or dynamic scaling) to add instances during peak hours and terminate them during quiet periods. This directly matches the described traffic pattern of weekday morning spikes and off-hour lulls, without manual intervention.
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 Reserved Instances
Why it's wrong here
Amazon EC2 Reserved Instances are a billing/pricing mechanism that applies a discounted hourly rate to matching instance configurations in exchange for a one- or three-year commitment. They do not alter the operation or scaling logic of an Auto Scaling group; the group still relies on its scaling policies to launch or terminate instances. Purchasing more Reserved Instances will not add instances or cause any scale-out event—they only reduce the cost of the instances that are already running.
- ✗
AWS Elastic Load Balancing
Why it's wrong here
Elastic Load Balancing (ELB) routes incoming application traffic across a set of healthy Amazon EC2 instances, providing fault tolerance and distributing load. However, ELB is not a scaling mechanism; it does not determine how many instances should exist and cannot itself launch or terminate instances. ELB integrates with Auto Scaling by acting as a traffic distributor and by feeding health/metering data into CloudWatch, which Auto Scaling policies can then use to make scaling decisions.
- ✓
Amazon EC2 Auto Scaling
Why this is correct
Amazon EC2 Auto Scaling is the correct answer because it is the service explicitly designed to maintain desired capacity and automatically adjust the number of EC2 instances in response to scaling policies. With a target tracking policy, for example, the Auto Scaling group continuously monitors a CloudWatch metric (like average CPU utilization) and proactively adds instances when the metric exceeds the target—this is scale-out—and removes them when it drops below. Scheduled policies also allow capacity to be added before predictable peaks, making it the only option that can directly execute a scale-out action.
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AWS CloudFormation
Why it's wrong here
AWS CloudFormation is a declarative infrastructure-as-code service that lets you model and provision resources such as Auto Scaling groups, load balancers, and instance configurations in a repeatable way. After the stack is deployed, CloudFormation does not perform ongoing capacity management; it only updates or deletes resources when you modify the template or delete the stack. To achieve dynamic scaling, you would use Auto Scaling policies and CloudWatch alarms, not CloudFormation, so it is not the service that triggers scale-out.
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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.