Multi-CDN Strategy & Failover Flashcards

Which metric should be the primary signal for performance-based CDN traffic steering in a multi-CDN system?

Answer: End-to-end time-to-first-byte (TTFB) measured from user locations

TTFB measured from actual user locations reflects real-world CDN performance and directly correlates with user experience quality.

A global e-commerce platform routes 70% of US traffic to CDN-A and 30% to CDN-B. CDN-A suffers a regional outage. What is the correct failover behavior if CDN-B is configured for active-active operation?

Answer: The traffic steering layer redirects 100% of US traffic to CDN-B automatically

An active-active system with automated steering detects the CDN-A outage and reroutes all affected traffic to CDN-B without operator intervention.

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.

What is the main risk of using extremely low DNS TTLs (e.g., 5 seconds) for multi-CDN failover?

Answer: Increased DNS resolver query load and potential rate limiting at authoritative nameservers

Very low TTLs dramatically increase DNS query frequency, which can overwhelm authoritative nameservers and DNS resolvers, creating a new point of failure.

A SaaS company needs its multi-CDN setup to comply with GDPR by ensuring EU user data does not transit through US CDN nodes. Which capability is required?

Answer: Geo-fencing and regional traffic isolation policies enforced at the DNS or CDN routing layer

Geo-fencing policies at the routing layer ensure EU user requests are only served by EU CDN nodes, keeping personal data within required jurisdictions.

Which CDN feature enables seamless content availability during a multi-CDN failover without requiring all traffic to hit the origin?

Answer: Origin shield (mid-tier caching)

An origin shield consolidates origin requests through a single mid-tier cache, so even during partial failovers, the shield can serve cached content to reduce origin load.

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.