Senior Full-Stack Engineer

IMPORTANT: We have attached the complete Product Requirements & Delivery Document of our platform to this job post. Please review the attached PDF first. The $500 test is specifically designed to prove you can handle the most complex modules of this document before we award the full $7,000+ contract. We are building a B2B2C Walled-Garden Marketplace in the Travel Tech industry. We have the full business logic, extreme architectural documentation (attached), and high-fidelity Figma designs ready. The total budget for the full project is $7,000 - $9,000. However, we do NOT award the full project blindly. We are hiring a Senior Tech Lead/Architect for a $500 paid test (Micro-Milestone 1) to prove you can master AI coding tools (Cursor/Windsurf) on complex logic, without the AI hallucinating. The $500 Test Task: You need to build a stripped-down, isolated Next.js API/backend proof-of-concept demonstrating you can handle the four core complexities of our attached PDF: Data Security (Supabase RLS): All tenant data (hotels, operators, orders) resides in shared tables. You must write native PostgreSQL Row Level Security (RLS) rules in Supabase to strictly isolate data at the database level. If Hotel A attempts to access Hotel B’s transactional data, the database itself must return zero rows, preventing any frontend bypass. Transactional Integrity (Saga Pattern): To prevent overbookings and double-charges across our B2B partners, you must implement a strict Saga Pattern: 1) Initiate a "Soft-Hold" on the ticket via a simulated API; 2) Authorize the user's card via Stripe (manual capture); 3) Confirm the ticket with the provider; 4) Capture the authorized Stripe funds. If any step fails, the system must automatically execute rollback procedures (cancel authorization or release hold). Financial Asynchrony (Escrow & Split Ledger): Funds must be held in the TSB platform account upon purchase. You must set up a robust scheduling architecture (cron jobs/ledger engine) that triggers exactly 48 hours after a simulated tour end-time. Upon trigger, the system must automatically calculate transaction fees, split the net payout, and transfer the correct splits (70% to Tour Operator, 10% to Hotel) to their respective Stripe Connected Accounts. Stateless Attribution (HTTP-Only Cookies): The B2C user experience must be frictionless, requiring zero login or registration. You must implement server-side stateless tracking using Signed HTTP-Only Cookies. This tracking must survive page refreshes, tab closures, and mobile OS background-app memory wipes, ensuring the correct hotel attribution is preserved and the 10% royalty is routed accurately at checkout. Who you are: You are not a junior prompt-engineer. You are a Senior Architect who uses AI to code 10x faster. You understand Database Security and Fintech architecture. LONG-TERM OPPORTUNITY (The Retainer): If you complete the full project successfully, on time, and within budget, we want to hire you on a long-term monthly retainer (fixed monthly salary) as our Fractional CTO / Lead System Maintainer. You will oversee the platform's stability, monitoring, and future micro-feature development. We are looking for a long-term partner. To apply: Review the attached PDF document. Start your proposal with the words 'WALLED GARDEN' (this filters out automated spam). Briefly explain in 2-3 sentences your architectural approach to handling the Saga Pattern rollback in Next.js. We are ready to hire the right partner immediately.