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PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications

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?

⚠ Common exam trap

Watch out — 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.

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

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.

Answer analysis

Option-by-option breakdown

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.

  • Cloud CDN

    Why this is correct

    Caches content, reducing load on backends and absorbing some attack traffic.

Visual reference

Source Router + ACL permit 10.0.0.0/8 deny any Server 10.0.0.5 ✓ 192.168.1.1 ✗ dropped ACLs evaluate top-down; first match wins — implicit deny all at end

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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.