CLF-C02 Billing, Pricing, and Support Practice Question

A company processes large amounts of data with Amazon EC2 and exports the results to customers globally via the internet. Which AWS cost component will be their largest variable cost?

⚠ Common exam trap

Watch out — candidates often assume inbound data transfer is costly or that inter-instance traffic incurs charges, but AWS specifically makes inbound free and same-AZ traffic free, so outbound internet transfer is the only significant variable cost among the options.

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

✓

Data transfer out of AWS to the internet (outbound)

Data transfer out of AWS to the internet (outbound) is typically the largest variable cost for workloads that export large results to global customers. AWS charges per GB for outbound data transfer, and rates increase with volume, while inbound data transfer is free. For a company processing large datasets on EC2 and sending results to customers via the internet, outbound traffic dominates the data transfer bill.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

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Data transfer into AWS (inbound)
Why it's wrong here
Data transfer into AWS from the internet is entirely free; AWS deliberately sets ingress pricing to zero to encourage customers to migrate and store data in the cloud. Uploading large datasets to Amazon S3 or EC2 incurs no data transfer charge, so this option cannot be a significant cost driver for an application that exports large amounts of data to end users. The only inbound charges you might encounter are for specific service features (e.g., certain AWS Marketplace or NAT gateway scenarios), but standard internet ingress remains free.
✓
Data transfer out of AWS to the internet (outbound)
Why this is correct
Data transfer out of AWS to the internet is metered per gigabyte and is the primary cost associated with exporting large amounts of data to end users. AWS uses a tiered pricing model where the per-GB rate decreases with monthly volume, but even at the lowest tiers, egress remains a substantial operational expense for data-intensive workloads. Services like Amazon S3, EC2, and CloudFront all apply this charge for data leaving AWS, which is why this is the correct answer.
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Data transfer between EC2 instances in the same Availability Zone
Why it's wrong here
Data transferred between EC2 instances in the same Availability Zone over private IP addresses is free because it stays entirely within AWS's internal network and never crosses a metered boundary. This is different from cross-AZ or cross-Region traffic, which incurs per-GB charges. If two instances are in the same AZ and communicate via private IPs, there is no data transfer cost, so this option cannot be the reason for high data export charges. (Note: using public or Elastic IPs for same-AZ traffic does incur charges, but the standard private path is free.)
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API calls to AWS services
Why it's wrong here
API calls to AWS services are typically billed per request, not per gigabyte of data transferred, making them a relatively minor cost compared to outbound data transfer. For example, Amazon S3 charges per 1,000 requests for PUT/GET/LIST operations, but these costs are negligible when compared to the per-GB egress fees for large-scale data export. While a high volume of API calls could add up, the dominant cost for an application serving large files to end users is always the network egress, not the control-plane or data-plane API request overhead.

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CLF-C02 Billing, Pricing, and Support Practice Question

Why each option matters

Option-by-option breakdown

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