The term “CDN” (“content delivery network”) conjures Google-scale companies managing huge racks of hardware, wrangling hundreds of gigabits per second. But CDNs are just web applications. That’s not how we tend to think of them, but that’s all they are. You can build a functional CDN on an 8-year-old laptop while you’re sitting at a coffee shop. I’m going to talk about what you might come up with if you spend the next five hours building a CDN.