CDN

TLDR: A CDN is a global network of edge servers. It caches content close to users to cut latency. CDNs also enforce geo-restrictions and bot filtering before requests reach the origin.

A content delivery network (CDN) is a geographically distributed group of servers. CDN nodes cache static assets — images, CSS, JavaScript, and video. When a user makes a request, the CDN routes it to the nearest edge node. This cuts round-trip time and speeds up page delivery. CDNs sit between the origin server and end users.

How a CDN Works

1. Caching: The CDN copies content from the origin to edge nodes worldwide.
2. Routing: DNS directs each request to the lowest-latency edge node.
3. Cache Hit: The edge node serves a fresh cached copy directly to the user.
4. Cache Miss: If not cached, the edge fetches from origin, caches the result, then serves it.
5. Cache Invalidation: Content refreshes on expiry or when the origin pushes an update.

Benefits of CDNs

1. Lower Latency: Edge servers are geographically closer to users. Load times drop significantly.
2. Higher Availability: Traffic spreads across many nodes. A single failure does not bring down the site.
3. Reduced Origin Load: The CDN absorbs most requests. The origin only handles cache misses.
4. DDoS Protection: CDNs absorb and filter large-scale attack traffic.
5. Geo-Restriction: CDNs block or restrict access based on the requester’s geolocation.

CDNs and Web Data Collection

Many websites delegate bot detection to their CDN edge layer. Requests flagged as non-human receive 403 or 503 responses before reaching the origin. Cloudflare alone protects a significant share of the web’s traffic in this way. Residential proxies route requests through real user IPs, bypassing CDN geo-blocks tied to datacenter IP ranges. Bright Data’s Web Unlocker handles CDN-level access controls and bot challenges automatically.

Major CDN Providers

1. Cloudflare: The most widely deployed CDN and bot-protection layer on the web.
2. Akamai: One of the largest CDN networks by infrastructure scale.
3. AWS CloudFront: Amazon’s CDN, tightly integrated with the AWS ecosystem.
4. Fastly: Known for real-time cache purging and edge computing capabilities.
5. Google Cloud CDN: Built on Google’s global network backbone.