Great question about the non-persistent game state — Implementing a custom setup on your own server is likely the best approach paired with CDN if alot of people are downloading.
SpacetimeDB 2.0 makes the database your game server.
You run game logic “inside” the DB, model world state as tables, and expose moves/damage/spawns as reducers. Clients (like Three.js) subscribe over WebSockets and get fine‑grained diffs instead of polling, so the server stays authoritative and the client just renders and interpolates. Generous free tier, paid starts at $25/month.