🏆 Day 2 of System Design — Leaderboard System Following @Striver_79's System Design Sheet and today hit the Leaderboard problem. Seems simple right? Just sort users by score. But at 50 Million DAU — nothing is simple. Here's what I learned today:

@striver_79 𝗪𝗵𝗮𝘁 𝗯𝗿𝗲𝗮𝗸𝘀 𝗳𝗶𝗿𝘀𝘁:❌ SELECT * ORDER BY score → full table scan on 50M rows ❌ Writing every score directly to MySQL → DB dies at 9K writes/sec ❌ No cache → 36K reads/sec killing your database