Content Delivery Network (CDN)
What Is a Content Delivery Network?
A Content Delivery Network (CDN) is a geographically distributed network of servers, called points of presence (PoPs), that cache and deliver web content from locations physically close to end users. Rather than every request traveling to a single origin server regardless of the user’s location, a CDN serves cached content from the nearest PoP, dramatically reducing latency and improving page load speed.
For global businesses with users in multiple regions, a CDN is not an optional performance enhancement; it is a fundamental infrastructure component that determines whether the website experience is acceptable or frustrating to international audiences.
What CDNs Cache and Deliver
CDNs are most effective with static content: images, videos, CSS stylesheets, JavaScript files, fonts, and downloadable documents. This content does not change per user and can be safely cached at edge locations without delivering stale or incorrect information. Dynamic content that is personalized per user typically bypasses CDN caches and is served directly from the origin, though advanced CDN configurations can partially cache dynamic responses as well.
CDN Benefits Beyond Speed
Reduced Origin Server Load
CDNs absorb the majority of traffic before it reaches the origin server. Serving a high-traffic website without a CDN requires the origin to handle every request. With a CDN, cache hit rates of 80 to 95 percent mean the origin only processes a fraction of total traffic.
DDoS Mitigation
CDN providers operate at a network scale that can absorb volumetric Distributed Denial of Service (DDoS) attacks that would overwhelm a single origin server. Many CDN providers include DDoS protection as a core service component.
SSL/TLS Termination
CDNs handle SSL/TLS certificate management and connection termination at the edge, offloading the computational overhead of encryption from the origin server.
Key Takeaways
- A CDN distributes content delivery across geographically dispersed edge servers to reduce latency for users worldwide.
- Static content including images, video, CSS, and JavaScript is most effectively cached and delivered by CDNs.
- CDNs reduce origin server load, improve availability, provide DDoS protection, and handle SSL/TLS termination.
- CDN performance is measured by cache hit rate, time to first byte (TTFB), and latency reduction compared to origin-only delivery.
- For globally distributed audiences, a CDN is an essential infrastructure for delivering an acceptable user experience.