CDN vs Direct Cost

CDN saves egress; adds CDN cost.

Overview

CDN trades origin egress for CDN egress at lower per-byte rates, plus the latency win. The math depends on cache-hit ratio: high hit rate makes the CDN dramatically cheaper than direct origin serving; low hit rate makes the CDN add cost without much benefit. The discipline is measuring the actual hit rate per region and tuning the architecture to where it pays back.

• CDN trades origin egress for CDN egress. Lower per-byte rates plus edge latency wins. The trade-off is cache-hit ratio.
• CDN versus origin egress per byte. Cost differential lives in the per-region pricing tables. Run the numbers.
• Cache hit rate. Headline metric. CDN economics depend almost entirely on this number.
• Per-region pricing plus quarterly cost review. Per-region egress costs differ; quarterly review catches drift between projected and actual hit rate.

The approach

Three habits keep CDN cost matched to actual savings: hit-rate measurement per region, per-region pricing analysis, and a quarterly review that prunes CDN spend that no longer pays back.

• Hit-rate driven decision. Measure actual hit rate per region. The CDN bill only makes sense at high hit rates.
• Per-region pricing. Egress costs differ per region. Architecture decisions reflect the math.
• Quarterly cost review. Catches drift; surfaces CDN spend that no longer pays back.
• CDN versus origin egress per byte plus documented rationale. Run the per-byte differential; per-CDN the architecture rationale documented.

Why this compounds

Each correctly-tuned CDN produces ongoing savings while keeping latency low for users. The team’s edge fluency deepens; new services arrive at CDN decisions on data instead of vendor decks.

• Cost efficiency. Right hit rate matched to workload cuts the egress bill.
• Latency improves. Right CDN places content closer to users. p99 drops.
• Operational fit. Right architecture matched to workload. CDN bill stays predictable.
• Year-one investment, year-two habit. First tuning is investment. By year two, every new service ships with CDN economics on day one.