Mixed Deck — All CDN Topics Flashcards

Which tool is most appropriate for diagnosing which CDN POP a specific end user is being routed to?

Answer: nslookup with the local resolver to identify the returned IP

Running nslookup or dig from the user's local resolver reveals the edge IP assigned by the CDN's Anycast or GeoDNS, identifying the serving POP.

What is 'cache warming' in the context of CDN monitoring, and when is it critical?

Answer: Pre-populating edge caches with content before a traffic event to prevent origin overload on cold caches

Cache warming involves pre-fetching content to edge nodes before high-traffic events (product launches, live streams) so initial requests are served from cache rather than overwhelming the origin.

Which TLS extension allows a CDN to serve multiple SSL certificates on a single IP address?

Answer: Server Name Indication (SNI)

SNI allows the client to send the requested hostname during the TLS handshake, enabling the server to select the correct certificate for that domain.

Why is scalability important in CDN architecture?

Answer: Handle growing traffic efficiently

Scalability is paramount in CDN architecture because web traffic can fluctuate dramatically, especially during peak events or viral content. A scalable CDN can efficiently handle a growing number of user requests and increasing data volumes without compromising performance. This ensures that content remains accessible and fast-loading, regardless of the demand, providing a consistent user experience.

Why is load balancing important in content distribution?

Answer: Distribute requests efficiently

Load balancing is essential in content distribution because it intelligently distributes incoming user requests across multiple CDN edge servers. This prevents any single server from becoming overwhelmed, which could lead to slow response times or service outages. By efficiently distributing the load, CDNs maintain optimal performance, high availability, and consistent content delivery speeds for all users, even during traffic spikes.

Which CDN billing model charges only when content is actually requested rather than reserving capacity in advance?

Answer: Pay-as-you-go (on-demand) pricing

Pay-as-you-go pricing charges based on actual usage, making it cost-effective for unpredictable or bursty traffic patterns.

How should CDN professionals handle confidential information related to multi-cdn strategy & failover?

Answer: Follow established protocols for data protection, access control, and disclosure in accordance with applicable regulations

Confidential information must be handled according to established protocols, regulatory requirements, and professional ethics standards, including proper access control and disclosure procedures.

Which CDN feature enables serving different content variants (e.g., mobile vs. desktop) from cache without separate origin requests for each?

Answer: Vary header-based caching

The Vary header instructs the CDN to cache separate versions of a response per header value (e.g., User-Agent), serving the correct variant from cache.

A CDN provider uses DNS-based load balancing to distribute users across PoPs. What latency metric does the DNS resolver typically use to select the nearest PoP?

Answer: RTT to the resolver's IP

CDN authoritative DNS servers measure round-trip time (RTT) from the resolver's IP to select the closest PoP.

A CDN-delivered API endpoint intermittently returns cached error responses (e.g., 500 errors) to clients. What configuration change would prevent this?

Answer: Configure the CDN to not cache 5xx responses (negative caching prevention)

By default some CDNs may cache error responses; explicitly configuring the CDN to bypass cache for 5xx status codes prevents error responses from being served to subsequent users.

Which CDN troubleshooting technique involves sending the same request from multiple geographically distributed vantage points simultaneously?

Answer: Synthetic monitoring with global probes

Synthetic monitoring with globally distributed probes sends identical requests from multiple locations to identify regional performance disparities or routing issues.

What role does continuous improvement play in video streaming & media delivery for CDN certified professionals?

Answer: It drives ongoing enhancement of practices, processes, and outcomes through systematic evaluation

Continuous improvement is fundamental to professional practice in video streaming & media delivery, involving regular evaluation, feedback integration, and process enhancement to maintain high standards.

Which CDN configuration setting controls how long a video segment is stored at an edge node before it is considered stale?

Answer: Cache TTL (Time-To-Live)

Cache TTL defines how long cached content remains valid at the edge before the CDN must revalidate or re-fetch it from origin.

Which content type is generally LEAST suitable for aggressive CDN caching with long TTLs?

Answer: Product listing pages with real-time inventory and pricing

Product pages with live inventory and pricing change frequently and vary per user, making long TTLs inappropriate without smart invalidation.

Which metric best measures the real-world performance improvement gained from moving business logic to the edge?

Answer: Time To First Byte (TTFB) decrease experienced by end users

TTFB directly reflects how quickly users receive the first byte of a response, making it the clearest indicator that edge processing reduced latency.

Which TCP optimization technique do CDN edges commonly use to improve throughput for users with high-latency connections?

Answer: TCP Fast Open and larger initial congestion windows

TCP Fast Open and increased initial congestion windows reduce the number of round trips needed before the connection reaches full throughput.

Which token or credential management practice is most critical when integrating multiple CDN APIs in a multi-CDN control plane?

Answer: Use a secrets manager with per-CDN scoped credentials and automatic rotation

A secrets manager with scoped, rotatable credentials limits blast radius if one CDN API key is compromised and enforces least-privilege access.

Which HTTP header should a CDN always strip from responses before caching to prevent leaking server-side implementation details?

Answer: X-Powered-By

The X-Powered-By header reveals backend technology (e.g., PHP/7.4, Express), providing attackers with information for targeted exploits; CDNs should strip it.

A CDN provider offers tiered API plans. Which rate limiting key granularity best supports per-plan enforcement?

Answer: API key or subscription tier identifier

Using the API key or subscription tier as the rate limit key allows distinct quotas to be applied per plan regardless of client IP.

A multi-CDN health check system reports 100% availability but users in Southeast Asia report slow load times from CDN-A. What type of monitoring gap does this scenario reveal?

Answer: Binary up/down health checks cannot detect performance degradation that falls short of complete failure

Traditional health checks only detect binary availability; they cannot identify latency degradation or partial performance issues that still return 200 OK responses.