How do you test application performance in a CDN-backed architecture?
- CDN
- caching
- edge performance
Answer it first, then compare. Nothing here is saved or scored.
Model answer
Test both cached and uncached scenarios: (1) Cache hit, verify CDN serves content quickly from edge. (2) Cache miss - test origin server performance when CDN cache is cold (purge cache before testing). (3) Cache invalidation - verify stale content is purged correctly. (4) Geographic distribution - run load tests from multiple regions to test CDN edge performance. (5) Dynamic vs. static - ensure CDN only caches appropriate content. (6) Cache thundering herd - many simultaneous cache misses for the same resource.
What interviewers listen for
- Workload modellingYou design the load shape from product traffic, not from tool defaults.
- Percentile literacyYou read p50/p95/p99 separately and explain why each matters.
- Bottleneck triageYou correlate metrics across application, database, and infrastructure layers.
- Capacity instinctsYou can translate a soak test into a sizing or scaling recommendation.