Senior Next.js/Supabase Developer — Ship Production Version of Real Estate Data Platform

I have a working full-stack web application — a data platform in the real estate / proptech space — and need a senior developer to harden it and ship a production version. It works end-to-end today; this is a finish-and-ship engagement, not a new build.Stack: Next.js (App Router, TypeScript), Supabase (Postgres + PostGIS, Storage — millions of rows), Vercel, multiple third-party data/mapping/AI APIs.Scope (milestone-based): Production authentication (replace a temporary gate with proper auth; role-ready) Caching + cost-control layer for third-party API usage (this is a core need) Reliability hardening — background jobs, retries, error monitoring One net-new data feature (spec provided at kickoff under NDA) Production deploy — custom domain, staging/prod separation, CI, docs You: 5+ yrs full-stack, strong Next.js App Router + TypeScript, real Postgres/PostGIS at scale (spatial queries on millions of rows), cost-aware API integration, milestone-driven, diagnose-before-fix, verify on deployed environments. Engagement: Milestone-based fixed price preferred. NDA + IP assignment required before any code access. Full context shared on kickoff call. To apply, answer (no answers = skipped): A production Postgres/Supabase system you built at 1M+ rows — what broke, how you fixed it. Your approach to caching third-party API responses/imagery to control cost (2–3 sentences). Rate limiting on Vercel serverless — what's wrong with in-memory counters, what do you use instead?