Quick Answer
The answer is Cloud Armor and Cloud CDN. Cloud Armor provides Web Application Firewall (WAF) capabilities with rate limiting and geo-based rules to filter malicious HTTP/HTTPS traffic at the application layer, directly mitigating HTTP flood DDoS attacks. Cloud CDN acts as a first line of defense by caching content at edge locations, absorbing volumetric attack traffic before it reaches the backend load balancer. On the Google Professional Cloud Developer exam, this pairing tests your understanding of layered defense: Cloud Armor handles the intelligent filtering, while Cloud CDN handles the scale absorption. A common trap is choosing only Cloud Armor and forgetting that CDN reduces origin load by serving cached responses, which is critical for high-volume floods. Memory tip: Armor filters the flood, CDN absorbs the volume—think “Filter and Absorb.”
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 uses Cloud Load Balancing to distribute traffic to HTTP backends. They want to protect against application-layer DDoS attacks (e.g., HTTP flood). Which TWO services should they combine?
Cloud Firewall rules
Why wrong: Network-layer filtering, not effective against application-layer attacks.
Cloud NAT
Why wrong: For outbound internet, not security.
Cloud Endpoints
Why wrong: Manages APIs, does not provide DDoS protection.
Cloud Armor
Provides rate limiting, IP blacklisting, and WAF rules to block HTTP floods.
Cloud CDN
Caches content, reducing load on backends and absorbing some attack traffic.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Cloud Armor
Cloud Armor is correct because it provides Web Application Firewall (WAF) capabilities and DDoS protection at the application layer, allowing you to create security policies that filter HTTP/HTTPS traffic based on IP addresses, geo-locations, or custom rules (e.g., rate limiting) to mitigate HTTP flood attacks. Cloud CDN is correct because it caches content at edge locations, absorbing a significant portion of malicious traffic before it reaches the backend, reducing the load on origin servers and acting as a first line of defense against volumetric application-layer attacks.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Cloud Firewall rules
Why it's wrong here
Network-layer filtering, not effective against application-layer attacks.
Cloud NAT
Why it's wrong here
For outbound internet, not security.
Cloud Endpoints
Why it's wrong here
Manages APIs, does not provide DDoS protection.
Cloud Armor
Why this is correct
Provides rate limiting, IP blacklisting, and WAF rules to block HTTP floods.
Related concept
Read the scenario before looking for a memorised answer.
Cloud CDN
Why this is correct
Caches content, reducing load on backends and absorbing some attack traffic.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often think Cloud Firewall rules (Option A) can block application-layer attacks because they confuse network-layer filtering with WAF capabilities, but Cloud Firewall cannot inspect HTTP payloads or apply rate limiting, making it unsuitable for HTTP flood protection.
Detailed technical explanation
Cloud Armor uses a set of security policies that are evaluated at the Google Cloud edge before traffic reaches the load balancer, allowing you to define rules based on Layer 7 attributes such as request headers, URI paths, and user-agents, and it supports pre-configured rules like XSS and SQL injection prevention. Cloud CDN leverages Google's global cache infrastructure to serve cached responses directly from edge locations, which not only improves latency but also effectively absorbs large volumes of attack traffic, as the cache can handle repeated requests without forwarding them to the backend. In a real-world scenario, combining these services allows you to use Cloud Armor's rate limiting to cap requests per client IP while Cloud CDN caches static assets, ensuring that even if the rate limit is exceeded, the cached content is still served without overwhelming the origin.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
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FAQ
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
The correct answer is: Cloud Armor — Cloud Armor is correct because it provides Web Application Firewall (WAF) capabilities and DDoS protection at the application layer, allowing you to create security policies that filter HTTP/HTTPS traffic based on IP addresses, geo-locations, or custom rules (e.g., rate limiting) to mitigate HTTP flood attacks. Cloud CDN is correct because it caches content at edge locations, absorbing a significant portion of malicious traffic before it reaches the backend, reducing the load on origin servers and acting as a first line of defense against volumetric application-layer attacks.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This PCD practice question is part of Courseiva's free Google Cloud 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 PCD exam.
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