The answer is data transfer out of AWS to the internet, which is typically the largest variable cost for workloads that export large results to global customers. This is because AWS charges per gigabyte for outbound traffic, and rates actually increase with the volume of data transferred, while all inbound data transfer into AWS is free. For a company processing massive datasets on Amazon EC2 and sending results to customers via the internet, outbound traffic will dominate the data transfer bill and quickly eclipse compute or storage costs. On the AWS Certified Cloud Practitioner CLF-C02 exam, this concept tests your understanding of the shared responsibility model and cost allocation—specifically that outbound data transfer is the only major variable cost that scales directly with customer usage. A common trap is confusing data transfer costs with storage costs or assuming inbound traffic is also charged. Remember the mnemonic: "Outbound is Outrageously Expensive; Inbound is Included."
CLF-C02 Billing, Pricing, and Support Practice Question
This CLF-C02 practice question tests your understanding of billing, pricing, and support. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Why wrong: Data transfer into AWS from the internet is free — it's outbound (egress) data transfer that incurs charges.
B
Data transfer out of AWS to the internet (outbound)
Outbound data transfer to the internet is charged per GB, making it a significant cost for applications that export large amounts of data to end users.
C
Data transfer between EC2 instances in the same Availability Zone
Why wrong: Data transfer between instances in the same AZ over private IP is free — only cross-AZ, cross-Region, and internet traffic incur charges.
D
API calls to AWS services
Why wrong: API calls are typically free or very low cost — data transfer costs are significantly larger for data-intensive export workloads.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Data transfer into AWS (inbound)
Why it's wrong here
Data transfer into AWS from the internet is free — it's outbound (egress) data transfer that incurs charges.
✓
Data transfer out of AWS to the internet (outbound)
Why this is correct
Outbound data transfer to the internet is charged per GB, making it a significant cost for applications that export large amounts of data to end users.
Related concept
Read the scenario before looking for a memorised answer.
✗
Data transfer between EC2 instances in the same Availability Zone
Why it's wrong here
Data transfer between instances in the same AZ over private IP is free — only cross-AZ, cross-Region, and internet traffic incur charges.
✗
API calls to AWS services
Why it's wrong here
API calls are typically free or very low cost — data transfer costs are significantly larger for data-intensive export workloads.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that 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.
Detailed technical explanation
How to think about this question
AWS charges for outbound data transfer at tiered rates (e.g., first 10 TB/month at $0.09/GB, next 40 TB at $0.085/GB, etc.), and these costs can escalate quickly for high-throughput workloads. In contrast, inter-AZ traffic within the same region is charged at $0.01/GB each way, but same-AZ traffic is free. This pricing asymmetry makes outbound internet transfer the primary cost driver for globally distributed data export use cases, especially when using EC2 instances with high network throughput like the c5n or m5n families.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CLF-C02 question in full detail.
Billing, Pricing, and Support — This question tests Billing, Pricing, and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this CLF-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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