System-design interview prep — concept mastery and full design reps.
- distributed_systems_prep_v2.html — systemDesingo: a Duolingo-style gamified app. 21 units (CAP, Replication, Consensus, Transactions, Concurrency, Partitioning, Caching, Time, Messaging, Load Balancing, Rate Limiting, Scalability, Reliability, Data Models, Batch/Stream, Trouble, Patterns, Framework, Decisions, Data/ML, Mock Designs). XP/levels, streaks, badges, boss battles + hearts, a Review-mistakes queue, and game modes: multiple-choice, swipe-to-sort, match, order, build, cloze (masked recall), "explain it out loud", and predict-then-reveal estimation. Full keyboard control (1–4 answer · Enter continue · Esc quit). Progress persists in localStorage.
- distributed_systems_prep.html — the encyclopedic v1 reference guide (cards, quizzes, interactive clock simulator, estimation scratchpad, worked exercises).
Open either file in a browser. No build step, no dependencies.