Baserates.dev – Programmer Napkin Math Trainer

A spaced repetition learning tool that helps developers memorize and internalize key performance metrics (latency numbers, throughput, etc.) through interactive flashcards. Developers can quiz themselves on systems knowledge that's critical for design decisions. Target: junior and mid-level engineers improving system design intuition.

System design interview prep is a growing market, driven partly by the proliferation of interview-focused platforms like Leetcode and the surge in engineers preparing for FAANG-style loops where back-of-envelope estimation is tested directly. No clear incumbent owns the spaced repetition niche for systems intuition specifically — Anki decks exist but are unsupported and scattered. The $500–2k/mo revenue band is realistic but requires either a sticky habit loop or a strong interview-anxiety angle to justify paid conversion, since the free alternative (a curated Anki deck) is always one GitHub search away. The core risk is that the addressable audience willing to pay is thin: engineers who care enough to drill latency numbers systematically are also the type to just build their own flashcard deck, and once interview season passes, churn will be brutal.