How to Build Your Own Global CDN Using Smart DNS and Anycast

How CDN Works

To deliver content quickly worldwide, the data should reside as close to the user as possible. Cheap virtual servers from many cloud providers can be placed in multiple regions, but simply adding a few servers is not enough; requests must be routed to the nearest server.

Speeding Up DNS

When a browser resolves a domain, it first performs a DNS lookup to obtain an IP address. A smart DNS server can perform a GeoIP lookup on the client’s IP and return the address of the nearest edge node, which is the core technique used by most commercial CDNs.

Why Not Use BGP Anycast?

Anycast requires control over network hardware and a pool of at least 256 IP addresses, exceeding typical budgets.

Anycast routing can be unstable; HTTP connections may drop if routes change mid‑transfer, adding complexity for large‑scale deployments.

Reducing hop count does not always reduce round‑trip latency; a single trans‑ocean hop can dominate response time.

Creating DNS Records

Since running a private BGP Anycast is impractical, the author chose Amazon Route 53 for latency‑based DNS routing (Dyn was too expensive; Route 53 offered a cheap alternative). After adding the domain, an A record is created for each edge server, pointing to its IP address. Health checks are recommended for each node to remove failed servers automatically.

Distributing Content

All edge nodes must hold identical content. For static sites generated by tools like Jekyll, a simple rsync command can copy the generated HTML files to every server. Dynamic platforms such as WordPress are more challenging because they cannot run directly on a CDN; a distributed storage solution would be required.

Using SSL/TLS Certificates

Each edge node needs a valid X.509 certificate for the domain. Let’s Encrypt can issue certificates automatically, but rate limits and certificate renewal issues (e.g., a London node being taken down before renewal) must be handled. The author uses Traefik as a reverse proxy, which supports distributed key‑value stores and can sync configuration via Apache Zookeeper.

Results

Performance testing shows the custom CDN delivers fast load times, though adding nodes in Asia and South America would further improve latency. After publishing the project on Hacker News, Google Analytics confirmed the improvements, with the author noting a need for a Singapore node because India’s load time exceeded the expected one‑second target.

Common Questions

Why not use CloudFlare? Commercial CDNs often evict rarely accessed content from cache, whereas a private CDN keeps all content cached.

Why not use S3/CloudFront? They lack support for custom cache headers and nice URLs without additional Lambda@Edge code, which suffers from cold‑start latency.

Why not use Google AMP? AMP only benefits traffic from Google Search, which is a small portion of the author’s audience.

Conclusion

Building a personal CDN is feasible and rewarding for developers who need globally fast access to their sites. The source code is available on GitHub for anyone to clone and deploy.