Senior Node.js/Postgres code and security review (AI booking assistant)

Senior engineer needed to find what's wrong with our code before real clients use it. About us We're an early-stage UAE startup building an AI booking assistant on WhatsApp for beauty salons. Clients book, move and cancel appointments by chatting in English and Arabic. The code is written with Claude, and we want an experienced engineer to challenge it. The job A fixed-price review of a private TypeScript codebase of about 2,000 lines, including one open pull request that adds Postgres storage. What to check - Double bookings, including two clients booking at the same moment - Whether one client could see or change another client's data - Leaks of names, phone numbers or other private data - How the AI acts on the booking system, and how it could be tricked - Whether the database design is ready for AWS What you'll deliver - Comments on the pull request - A one-page summary, ranked from most to least serious, in plain English for a non-technical founder What we're looking for - Production experience with Node.js, TypeScript and Postgres - Production experience on AWS - Strong security judgement - Working hours within a few hours of Dubai (UTC+4) - Nice to have: WhatsApp Cloud API, Claude API or Arabic What comes next If this goes well, we'd like to keep working with you on a part-time monthly retainer: reviewing changes before they go live and being on call during our pilot. How to apply An NDA is required before you get access to the code. Please skip the generic cover letter and answer these three questions in your own words: 1. What's the first thing you'd check to stop double bookings? 2. What's the best bug or security issue you've ever caught? 3. How many hours would this review take you?