CDN (Content Delivery Network)

What is a CDN?

A content delivery network is a global fleet of servers that cache copies of your content close to where people actually are. When someone in Tokyo loads a site whose origin server sits in Virginia, a CDN serves the images, scripts, and often the pages themselves from a nearby edge location instead of routing every byte across the planet. Less distance means lower latency and a faster page.

CDNs cache static assets well by default: images, fonts, CSS, JavaScript, video. With the right rules they also cache full HTML pages and API responses. They absorb traffic spikes, shield the origin from load, and provide a first line of defense against denial-of-service attacks. The core challenge is invalidation: when content changes, stale copies have to be purged or they keep serving old data. A retailer running a flash sale leans entirely on its CDN, because the origin server alone could never handle a million shoppers hitting the same product page at once.

Cloudflare, Fastly, Amazon CloudFront, and Akamai are common providers. Modern edge platforms go further, running code at edge locations, not just caching files.

CDNs at Dallonses

A CDN is one of the highest-leverage moves in performance work, and one of the easiest to misconfigure. We have seen sites pay for a CDN that cached almost nothing because the cache headers told it not to, and sites that cached too aggressively and served logged-in users each other's data. Getting the cache rules right per route is detailed work, and it is where our performance testing and monitoring earns its keep.

We treat the CDN as part of the architecture, not an afterthought toggled on at launch. That means deliberate cache keys, clean invalidation tied to content changes, and a clear split between what the edge serves and what the origin owns. Done well it also cuts infrastructure spend, since the origin does far less work, which is where this overlaps directly with our cost optimization practice.

Site slow for users far from your servers, or bills climbing as traffic grows? Let's look at your edge setup.

Talk to us about performance