Next.js 15 + Supabase: I Accidentally Blew Past My Quota by 1000% (and How “Local‑First” Saved It)

TL;DR: My “perfectly reasonable” real-time architecture for an online party game turned into a billing horror story — first with Supabase Realtime broadcasts, then with Redis + polling. The fix wasn’t “optimize the server.” It was stop needing the se...