This CCSP practice question tests your understanding of cloud application security. 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 global e-commerce platform uses AWS API Gateway to expose REST APIs to third-party developers. The security team notices that a malicious user is repeatedly sending large payloads to a /submit endpoint, causing high CPU usage on backend Lambda functions. The API uses a simple API key for authentication. Which combination of controls should be implemented to mitigate this attack while preserving legitimate access?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure API Gateway throttling and request body size validation
Option A is correct because it directly addresses the two attack vectors: large payloads causing CPU exhaustion and excessive request volume. API Gateway request body size validation (up to 10 MB by default, configurable) rejects oversized payloads before they reach the backend Lambda, while throttling (e.g., 10,000 requests per second with a burst limit) prevents a single user from overwhelming the system. Together, these controls preserve legitimate access by only limiting anomalous traffic, not blocking all users.
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.
✓
Configure API Gateway throttling and request body size validation
Why this is correct
Throttling limits request rate, and size validation rejects large payloads before reaching Lambda.
Related concept
Read the scenario before looking for a memorised answer.
✗
Subscribe to AWS Shield Advanced for DDoS protection
Why it's wrong here
Shield Advanced is for large DDoS, not for application-level abuse on a single endpoint.
✗
Change authentication to IAM roles with temporary credentials
Why it's wrong here
Better auth does not prevent volumetric attacks.
✗
Enable AWS WAF with a rate-based rule and block IP addresses
Why it's wrong here
WAF rate-based rules can throttle but do not limit payload size.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the distinction between network-layer DDoS protection (Shield Advanced) and application-layer controls (throttling, WAF, payload validation), leading candidates to choose Shield Advanced when the attack is clearly at the application layer.
Detailed technical explanation
How to think about this question
API Gateway throttling operates at the account and stage level, using a token bucket algorithm with a configurable rate limit and burst capacity—excess requests receive a 429 Too Many Requests response, which the client can retry after a backoff period. Request body size validation is enforced at the API Gateway layer before any integration request is sent, meaning Lambda functions are never invoked for oversized payloads, directly reducing CPU usage. In a real-world scenario, a malicious actor could rotate IP addresses to bypass IP-based blocking, making rate-based rules less effective, whereas throttling and payload validation are agnostic to the source IP.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Cloud Application Security — This question tests Cloud Application Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure API Gateway throttling and request body size validation — Option A is correct because it directly addresses the two attack vectors: large payloads causing CPU exhaustion and excessive request volume. API Gateway request body size validation (up to 10 MB by default, configurable) rejects oversized payloads before they reach the backend Lambda, while throttling (e.g., 10,000 requests per second with a burst limit) prevents a single user from overwhelming the system. Together, these controls preserve legitimate access by only limiting anomalous traffic, not blocking all users.
What should I do if I get this CCSP 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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Question Discussion
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