When I began my career in programming I remember reading Jeff Dean's "Latency Numbers Every Programmer Should Know" [1], and getting inspired. Alas, it's been over a decade, and I never fully internalized all the numbers.Until recently. I discovered Simon Eskildsen's talk [2] and github repo [3] on programmer napkin math. I liked his reasoning, and decided to _actually_ internalize the numbers now.So I made baserates.dev.It's a spaced repetition program that teaches you the napkin math from Simon, enhanced with a few things from Jeff Dean's list. The main changes: I included CPU instructions, like L1 Cache reads. I also included some nooby context, like how to pronounce the character μ, and a reminder on what is bigger: nano seconds, or micro seconds.The app automatically saves your progress, and doesn't require auth. Most of the logic is vibe coded: I fed Claude all the links. I use InstantDB [^4] for the backend, mainly to support guest auth and saving progress. Most of my time spent...