IntermediateScenario
10 min
Slow CDN Performance
CDNNetworkingPerformance
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Interview Question
Users in one region report very slow page loads, but the rest of the world is fine. How do you troubleshoot this CDN performance issue?
Key Points to Cover
- Check CDN logs and edge metrics for affected region
- Validate DNS/geolocation routing correctness
- Check origin health and caching headers
- Work with CDN provider for routing/failover
- Add synthetic tests for regional coverage
Evaluation Rubric
Uses CDN metrics/logs to scope issue30% weight
Validates DNS/geo-routing correctness30% weight
Checks origin caching/headers20% weight
Engages CDN provider effectively20% weight
Hints
- 💡Regional issues often due to ISP peering/CDN PoP outages.
Common Pitfalls to Avoid
- ⚠️Focusing solely on the origin server and neglecting CDN-specific logs and metrics.
- ⚠️Assuming DNS is always correct and not validating geolocation routing.
- ⚠️Not examining caching headers diligently, which can cause frequent origin fetches.
- ⚠️Ignoring the CDN provider's own performance dashboards and edge-specific metrics.
- ⚠️Performing generic network tests without targeting the specific affected region or CDN endpoints.
Potential Follow-up Questions
- ❓How to add proactive regional monitoring?
- ❓How do you handle CDN failover?
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