CDN (Content Delivery Network)
What is it?
A Content Delivery Network is a globally distributed network of servers that stores (caches) copies of website content closer to users. Instead of every visitor fetching files from a single origin server in, say, Virginia, Cloudflare serves cached content from whichever of its 300+ data centers is closest to the user. This is the core of what made Cloudflare famous.
What problem does it solve?
- Latency: The further data travels, the slower it loads. A user in Tokyo shouldn't have to wait for a response from a server in New York.
- Origin load: Without a CDN, every request hits your origin server. During traffic spikes, this can overwhelm and crash it.
- Cost: Bandwidth from cloud providers (AWS, GCP, Azure) is expensive. Cloudflare absorbs that traffic at its edge, often dramatically reducing cloud egress bills.
How does it work?
- A customer's website is set up behind Cloudflare (via DNS).
- When the first user requests a page, Cloudflare fetches it from the origin server and caches a copy at the edge data center nearest to the user.
- Subsequent users in that region get the cached copy directly from the edge — no round trip to the origin.
- Cache rules and TTLs (Time-to-Live) determine how long content stays cached and what gets cached.
- Cache Reserve uses R2 storage as a persistent upper-tier cache, reducing origin pulls even further.
Key concepts:
- Cache HIT: Content served from the edge (fast).
- Cache MISS: Content fetched from origin (slower, then cached).
- Tiered Cache: Cloudflare data centers can check a regional "upper-tier" cache before going all the way to the origin.
Why it matters strategically
The CDN is Cloudflare's original product and remains central to its value proposition. It's the reason companies first adopt Cloudflare — faster websites, lower bandwidth bills, and better uptime. It's also the product that established Cloudflare's massive global network, which is now the platform for everything else (security, Zero Trust, developer tools).