Content Delivery Network (CDN)
A geographically distributed network of proxy servers that deliver content from locations closest to the user, reducing latency and improving load times.
§ 1 Definition
A Content Delivery Network (CDN) is a distributed network of edge servers that cache and serve static and dynamic content from locations geographically close to end users. By reducing the physical distance between user and server, CDNs dramatically reduce TTFB and improve LCP, especially for global audiences. CDNs also absorb traffic spikes, mitigate DDoS attacks, and often provide image optimization, compression, and HTTP/2 support.
§ 2 How CDNs Work
CDNs deploy hundreds or thousands of points of presence (PoPs) worldwide. When a user requests content, the CDN routes to the nearest PoP. Cached responses (static assets, cached pages) are served directly from the edge. Dynamic content is forwarded to the origin server but connections benefit from optimized routing, keep-alive, and TLS termination at the edge.
§ 3 Common Misunderstandings
A CDN is NOT just a caching layer. It provides connection optimization (TLS termination at edge, HTTP/2 multiplexing, TCP optimizations), DDoS protection, image transformation (on-the-fly resize, format conversion), and edge compute (serverless functions at PoPs). Also, a CDN does not automatically make a slow site fast: if the origin server is slow and uncacheable, the CDN can hide only the network latency, not the server processing time.
§ 4 Choosing a CDN
Consider geographic coverage (do they have PoPs in the regions your users are?), performance (TTFB benchmarks), features (image optimization, edge compute, WAF), and pricing (bandwidth vs request-based). Leading providers: Cloudflare, Fastly, Akamai, AWS CloudFront, Bunny.net, and KeyCDN. Many offer free tiers for basic use.
§ 5 Note
§ 6 In code
# Typical DNS setup
# CNAME your assets domain to the CDN endpoint
assets.yourdomain.com CNAME yourcdn.example.com
# Then reference via
<img src="https://assets.yourdomain.com/hero.webp">§ 7 Common questions
- Q. Does a CDN help with dynamic content?
- A. Partially. For uncacheable content, the CDN provides connection optimization (TLS, HTTP/2, optimized routing) but does not cache the response.
- Geographically distributed caching and delivery.
- Reduces TTFB and improves LCP.
- Provides DDoS protection and image optimization.
- Essential for global audiences.
Atomic Glue selects, configures, and optimizes CDN deployments tailored to each client's audience geography and content profile. Web Development services.
Get in touchA geographically distributed network of proxy servers that deliver content from locations closest to the user, reducing latency and improving load times.
Category: Performance (also: Infrastructure)
Author: Atomic Glue Performance Team
## Definition
A Content Delivery Network (CDN) is a distributed network of edge servers that cache and serve static and dynamic content from locations geographically close to end users. By reducing the physical distance between user and server, CDNs dramatically reduce TTFB and improve LCP, especially for global audiences. CDNs also absorb traffic spikes, mitigate DDoS attacks, and often provide image optimization, compression, and HTTP/2 support.
## How CDNs Work
CDNs deploy hundreds or thousands of points of presence (PoPs) worldwide. When a user requests content, the CDN routes to the nearest PoP. Cached responses (static assets, cached pages) are served directly from the edge. Dynamic content is forwarded to the origin server but connections benefit from optimized routing, keep-alive, and TLS termination at the edge.
## Common Misunderstandings
A CDN is NOT just a caching layer. It provides connection optimization (TLS termination at edge, HTTP/2 multiplexing, TCP optimizations), DDoS protection, image transformation (on-the-fly resize, format conversion), and edge compute (serverless functions at PoPs). Also, a CDN does not automatically make a slow site fast: if the origin server is slow and uncacheable, the CDN can hide only the network latency, not the server processing time.
## Choosing a CDN
Consider geographic coverage (do they have PoPs in the regions your users are?), performance (TTFB benchmarks), features (image optimization, edge compute, WAF), and pricing (bandwidth vs request-based). Leading providers: Cloudflare, Fastly, Akamai, AWS CloudFront, Bunny.net, and KeyCDN. Many offer free tiers for basic use.
## Note
CDNs are essential for global audiences but add marginal latency for local requests. Always test TTFB from representative user locations.
## In code
# Typical DNS setup # CNAME your assets domain to the CDN endpoint assets.yourdomain.com CNAME yourcdn.example.com # Then reference via <img src="https://assets.yourdomain.com/hero.webp">
## Common questions
Q: Does a CDN help with dynamic content?
A: Partially. For uncacheable content, the CDN provides connection optimization (TLS, HTTP/2, optimized routing) but does not cache the response.
## Key takeaways
- Geographically distributed caching and delivery.
- Reduces TTFB and improves LCP.
- Provides DDoS protection and image optimization.
- Essential for global audiences.
## Related entries
- [Edge Caching](atomicglue.co/glossary/edge-caching)
- [Browser Caching](atomicglue.co/glossary/browser-caching)
- [TTFB (Time to First Byte)](atomicglue.co/glossary/ttfb-time-to-first-byte)
Last updated July 2026. Permalink: atomicglue.co/glossary/content-delivery-network-cdn