Price Azure CDN or Front Door egress and requests, and value the origin bandwidth your cache hit ratio saves.
A CDN replaces expensive origin egress with cheaper edge egress, but only for the fraction it can cache — every miss pays both the CDN rate and the origin egress rate for the same byte. That makes the cache hit ratio the single most important input: at 92% the double-charged share is small, at 50% the CDN can cost more than serving directly. Cache-control headers and query-string handling are what actually move the hit ratio, so tuning them is a cost lever rather than a performance nicety; CDN egress is priced by geographic zone and volume band, so confirm the rates for the regions your users are in with the Azure pricing calculator.
Azure CDN Cost
origin traffic = delivered GB × (1 − cache hit ratio); monthly = delivered GB × CDN price + origin GB × origin egress price + requests ÷ 10,000 × request price + base fee.
origin traffic = delivered GB × (1 − cache hit ratio); monthly = delivered GB × CDN price + origin GB × origin egress price + requests ÷ 10,000 × request price + base fee. A CDN replaces expensive origin egress with cheaper edge egress, but only for the fraction it can cache — every miss pays both the CDN rate and the origin egress rate for the same byte. That makes the cache hit ratio the single most important input: at 92% the double-charged share is small, at 50% the CDN can cost more than serving directly.
Cache-control headers and query-string handling are what actually move the hit ratio, so tuning them is a cost lever rather than a performance nicety; CDN egress is priced by geographic zone and volume band, so confirm the rates for the regions your users are in with the Azure pricing calculator.
This calculator takes 7 inputs: Data delivered to clients, CDN egress price per GB, Cache hit ratio, Origin egress price per GB, Requests, Price per 10,000 requests, Profile base fee. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.