Single-table DynamoDB design for a real-time game (rooms, rounds, leaderboards)

For the H0 Hackathon I built Kauwa Udd, a real-time multiplayer reaction game on Vercel + Amazon DynamoDB. People hear "DynamoDB" and reach for a table per entity — users table, rooms table, scores table. I put everything in one table. Here's the design, why it works for a live game, and the exact k