15Design a real-time leaderboard for a mobile game with ten million daily players.▼easyNewFlipkartPhonePeSwiggy○ sign inThe vocabulary question hiding real depth: which primitive replaces ORDER BY, why sharding by player is wrong, and what a 45,000 updates-per-second storm actually costs.Open full answer →
18Postgres is out of headroom. How do you choose a shard key, and how do you reshard later without downtime?▼hard★ EssentialNewPhonePeFlipkartUber○ sign inSharding buys write headroom and bills you in joins, foreign keys, and every future migration. The key choice is a query-pattern bet; the resharding choreography separates operators from diagram artists.Open full answer →
