Backend developer for multi-tenant SaaS dashboard (Supabase + React + OAuth integrations)

Job description: We have a complete frontend dashboard built in React + Vite + TypeScript + Tailwind. It's a single-pane-of-glass for tradespeople — they log in and see their invoices, emails, calendar, leads/opportunities, revenue vs last FY, and an interactive job map. The UI is done and running on mock data. We now need the backend built so it works with real data. What we need built: Multi-tenant auth — separate logins per user. Each user's data fully isolated. Starting with ~100 users, scaling to 1000+. We're leaning toward Supabase (Postgres + Auth + Row-Level Security) but open to your recommendation. OAuth integrations — users click "Connect" on Xero, Stripe, Google Calendar, Gmail, a CRM, and job-management tools (Jobber/SimPRO). Handle the OAuth flow and store each user's access/refresh tokens securely (encrypted at rest). Scheduled sync — a cron job (every 30 min) per user that pulls fresh data from each connected integration and normalizes it into our schema. Must handle token refresh, rate limits, and failures gracefully. API layer — REST or tRPC endpoints the frontend calls to read invoices, leads, events, emails, revenue aggregates, etc. All scoped to the authenticated user. Storage — Postgres tables for users, integrations/tokens, invoices, leads, calendar events, emails, jobs. Plus aggregation logic for dashboard summary cards (revenue, gross profit, win rate, outstanding invoices, etc.). Scalability — must handle 1000+ concurrent users without rewrites. Prefer a managed platform (Supabase / Vercel serverless) over self-hosting. Tech stack we're considering: Supabase (Postgres + Auth + Edge Functions for cron sync), Vercel for frontend hosting, React Query on the frontend for caching. Open to alternatives if you have a better fit. Requirements: Proven experience with Supabase or equivalent BaaS Proven OAuth integration experience (Xero, Stripe, Google APIs) Experience building multi-tenant SaaS with proper data isolation Strong English communication Available to start within 2 weeks To apply, please include: Links to 2–3 similar projects you've built (multi-tenant SaaS, OAuth integrations, or Supabase backends) Your recommended stack and why Confirmation you can hit the milestone structure above Your hourly rate and availability (hours/week) We'll provide the full frontend code and a wireframe of every screen so you can see exactly what data the backend needs to serve.