How do you measure CDN performance?

CDN performance is measured through metrics like Time to First Byte (TTFB), cache hit ratio, origin offload percentage, bandwidth savings, latency by geographic region, and error rates. Tools like Real User Monitoring (RUM), synthetic testing, and CDN analytics dashboards provide comprehensive performance visibility.

What are Core Web Vitals and how do CDNs affect them?

Core Web Vitals are Google's metrics for user experience: Largest Contentful Paint (loading), Interaction to Next Paint (interactivity), and Cumulative Layout Shift (visual stability). CDNs improve LCP by serving content from nearby edge servers, reduce INP through faster asset delivery, and help CLS by enabling proper resource dimensioning.

How does image optimization work on a CDN?

CDN image optimization automatically converts images to modern formats like WebP or AVIF, resizes them based on device viewport, adjusts quality levels, and strips unnecessary metadata. This happens at the edge in real-time, reducing image payload sizes by 40-80% without requiring changes to the origin server.

What is HTTP/3 and how does it improve CDN performance?

HTTP/3 uses the QUIC protocol over UDP instead of TCP, eliminating head-of-line blocking and reducing connection setup time. CDNs implementing HTTP/3 deliver faster page loads especially on mobile networks, better performance during packet loss, and quicker connection establishment through 0-RTT handshakes.

How do you optimize CDN cache performance?

CDN cache optimization involves maximizing cache hit ratios through proper TTL configuration, normalizing cache keys to avoid unnecessary variants, implementing stale-while-revalidate headers, using origin shields to consolidate cache fills, and regularly analyzing cache analytics to identify and fix low-hit-ratio content.

CDN Performance: Speed, Compression, and Core Web Vitals

September 25, 2026 · FlyFish NWA Editorial

Performance is the primary reason organizations adopt CDNs. This cluster covers every performance optimization technique — from protocol-level tuning to content optimization and real user monitoring.

Latency OptimizationReducing time-to-first-byte and beyond.
Brotli & Gzip CompressionCompressing content for faster delivery.
Image OptimizationResponsive images, WebP, AVIF at the edge.
HTTP/2, HTTP/3 & QUICModern protocols for faster delivery.
Prefetch & PreloadBrowser hints for faster loading.
Core Web VitalsCDN's impact on LCP, FID, CLS.
Video DeliveryStreaming and VOD optimization.
Performance MetricsKey metrics for CDN performance.
HTTP 103 Early HintsPre-sending resource hints.
Real User MonitoringMeasuring actual user experience.
Log AnalysisAnalyzing CDN logs for optimization.

This topic cluster contains 11 articles progressing from foundational concepts to advanced implementations. Read them in order for a comprehensive understanding, or jump to any topic that interests you.

Figure 1: CDN Network Architecture — Content delivery flow from origin to edge

External References

RFC 9110: HTTP Semantics
W3C Resource Timing Specification
HTTP Archive: State of the Web

Performance Comparison: Edge vs Origin Processing
Metric	Edge Processing	Origin Processing	Improvement
Latency (p50)	8–15 ms	120–300 ms	15–20x faster
Cache Hit Ratio	85–95%	N/A	Reduces origin load
TLS Handshake	1–5 ms (nearby PoP)	50–150 ms	10–30x faster
Bandwidth Cost	$0.01–0.04/GB	$0.05–0.12/GB	3–5x cheaper
Availability	99.99% (multi-PoP)	99.9% (single DC)	10x fewer outages

Articles in This Cluster

Continue Reading: Performance & Optimization

Explore Other Topics

External References