A team is sizing an EC2 instance for a small internal wiki. It is idle for most of the working day and gets short bursts of use when someone searches it. Which TWO statements should guide the decision?

AWS Certified Cloud Practitioner (CLF-C02), objective 3. Cloud technology and services medium

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The options

Choose 2.

Correct A burstable general purpose instance accumulates credits while it is idle and spends them during bursts, which matches this usage profile

Correct. The burstable T family is built for workloads with a low average and occasional peaks — precisely this one — and it costs far less than an instance sized for the peak.

Correct If the choice turns out to be wrong, the instance type can be changed later by stopping the instance and starting it on a different type

Correct, for an EBS-backed instance. That is what makes rightsizing an ongoing activity rather than a decision you must get perfect on day one.

Not correct The instance type is fixed for the life of the instance, so it must be sized for the worst case now

Wrong, and it is the belief that causes systematic overprovisioning. Being able to resize is one of the differences between renting capacity and buying a server.

Not correct Choosing a larger size is safe because AWS charges per instance rather than per size

Wrong. Price scales with size — roughly double the size, roughly double the hourly rate. Oversizing is the most common avoidable EC2 cost there is.

Not correct A compute optimized instance is required so that the wiki responds quickly when someone does use it

Wrong. Responsiveness comes from having enough capacity at the moment of use, which burst credits provide. Compute optimized is for sustained processor-bound work, and here the processors would sit idle nearly all day.

Why

Rightsizing means matching the instance to the workload's real shape and revisiting that as the workload changes — helped by CloudWatch metrics and by AWS Compute Optimizer's recommendations. Two properties make it possible: the burstable families price an idle-with-spikes profile honestly, and an EBS-backed instance can be moved to another type with a stop and a start. Neither is available when you have bought a physical server.

Where this comes from

Cited
AWS exam guide task statement 3.3

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