CDN Performance Impact

Latency improvement.

Overview

CDN performance is what the CDN actually delivers, measured under real traffic. Vendor claims live in marketing; real impact lives in RUM data and cache-hit telemetry.

• Latency improvement. Per-region, per-asset latency reduction measured against origin-only baseline.
• Cache hit rate. The headline metric. CDN economics depend almost entirely on the hit ratio.
• Origin offload. Bytes served from edge versus origin. Drives the cost story directly.
• Tail latency plus RUM. p99 and p99.9 reduction matter more than median; RUM data confirms or refutes the synthetic numbers.

The approach

Three habits keep CDN measurement honest: RUM is the source of truth, measure per-region, and document the methodology so future comparisons stay apples-to-apples.

• RUM-driven. Real user monitoring confirms or refutes synthetic Lighthouse runs. RUM is the production reality.
• Per-region measurement. Edge proximity matters. North America numbers do not represent Asia or Europe.
• Cache hit rate per asset and version. The hit ratio decides the cost story. Track it per asset class to find the weak spots.
• Documented methodology. Future measurements stay apples-to-apples when the methodology is written down.

Why this compounds

Each measured optimisation produces ongoing user-experience and cost benefit. The team learns the edge through measurement, not through vendor decks.

• Better user experience. Lower latency produces measurable engagement and conversion gains.
• Cost efficiency. High cache hit ratio reduces origin compute and egress cost. The savings continue every month.
• Resilience. Edge absorbs origin issues during incidents. Caching becomes part of the availability story.
• Year-one investment, year-two habit. The first measurement methodology takes effort. By year two, every CDN change is measured against the same baseline.