Senior Backend Developer Needed for Fintech Waitlist, Referral, Rewards, and User Tracking System

Job Overview We are seeking an experienced backend developer to build a robust and scalable backend system for a fintech waitlist platform. This project goes beyond a simple landing page or email capture form. We need a backend infrastructure that supports: - waitlist signups - referral tracking - coin-based rewards - cash-based referral rewards - user dashboard data - automated email delivery - user location tracking - internal reporting and database visibility - future migration into the full app at launch We are looking for a developer who can think strategically, structure the system cleanly, and build something that is reliable, extensible, and launch-ready. Project Overview We are building a pre-launch waitlist experience for a fintech product. The system should allow users to join early, complete their profile, refer friends, earn rewards, and later transition into the main app once it launches. This backend will power the full waitlist and referral journey. Project Scope We need a backend system that supports the following user flow and business logic: 1. Waitlist Signup A user joins the waitlist by entering their email address. Once this happens, the system should: - create a new user record - prevent duplicate registrations - assign 100 Coins - generate a unique referral code / referral link - trigger an automated welcome email - include a personalized dashboard link in that email 2. Profile Completion Reward After signup, the user may complete their profile by entering: - full name - phone number Once both fields are successfully submitted and saved, the system should: - update the user record - award an additional 400 Coins - ensure this bonus is only granted once - update the user’s dashboard / reward totals 3. Referral Reward System Each user should have a unique referral link. When a referred user signs up through that link, the system should track the referral and award the referring user: - 500 Coins per referral - $20 cash per referral The backend must keep a clear record of: - who referred whom - which referrals converted - how many coins were earned from referrals - how much cash was earned from referrals - referral status and timestamps We want the logic to be designed carefully so the system can avoid duplicate credits, self-referrals, or inaccurate tracking wherever possible. 4. Coin Milestones / Reward Logic The coin system should support the following reward milestones: - 2,500 coins = 2 months free premium membership - 3,000 coins = 3 months free premium membership The backend should track each user’s total coin balance and progression toward these milestone rewards. 5. Automated Welcome Email After initial signup, the system should automatically send a welcome email that includes: - confirmation that the user joined the waitlist - their personalized dashboard link - an overview of how rewards work - information on how to earn more coins and cash Please recommend the email service/provider you would use and explain why. 6. Dashboard Data Each user should have a backend-supported dashboard record showing, at minimum: - email - full name - phone number - signup date - profile completion status - referral code - referral link - total coins earned - total cash earned - number of successful referrals - milestone progress - location/source of signup 7. Admin Visibility / Reporting We need the data structured so our internal team can review and analyze waitlist performance. At minimum, we need visibility into: - total signups - completed profiles - referral activity - top referrers - total coins issued - total cash rewards earned - signup source/location data - conversion trends If you also have experience building a lightweight internal admin dashboard or reporting layer, please mention that. 8. Location Tracking The system should identify where users signed up from. At minimum, we want to capture: - city - state - country - IP-based location (if appropriate) Please explain the best method you would use for this and the expected reliability. 9. Future Migration Into the Main App This waitlist database will eventually support onboarding when the full app launches. For that reason, the backend should be structured so user data can later be reused or migrated, including: - account information - referral history - coin balances - earned cash values - profile data - signup source/location data What We Want From the Developer We are looking for someone who can do more than just build endpoints. We want someone who can: - think through the system architecture - structure the database intelligently - propose reliable backend logic - explain tradeoffs clearly - anticipate edge cases - build with future growth in mind Proposal Requirements To be considered, please provide a thoughtful response that includes the following: 1. Step-by-Step Build Approach Please explain clearly how you would build this system from start to finish, including: 1. database structure 2. waitlist signup flow 3. rewards logic 4. referral tracking logic 5. coin and cash calculations 6. email automation 7. dashboard data structure 8. location tracking 9. admin/internal reporting 10. future migration approach We are specifically looking for a clear process, not just a short note saying you can handle it. 2. Similar Work Please provide strong examples of similar work, especially projects involving: - referral systems - waitlist systems - rewards or loyalty systems - user dashboards - fintech-related backend work - onboarding/email workflows - database-driven admin/reporting tools Please be specific about: - what the project was - what your role was - what technologies were used - what parts of the system you personally built 3. Tech Stack Recommendation Please tell us what stack you recommend for this project and why. Examples may include: - Node.js / NestJS / Express - Python / Django / FastAPI - PostgreSQL / Supabase / Firebase - AWS / Vercel / Railway / Render - SendGrid / Postmark / Resend - geolocation / analytics services - admin/reporting tools You do not need to use these exact technologies, but you should explain what you believe is best. Ideal Candidate The ideal developer will have strong experience with: - backend system design - referral and rewards logic - secure user data handling - transactional email systems - reporting/analytics-friendly databases - scalable architecture - fintech or consumer-product workflows Deliverables At minimum, we expect: - backend architecture - database schema - reward and referral logic - email automation setup - user tracking and location capture - API endpoints / backend services - dashboard-ready data support - clean documentation for handoff Bonus if you can also help with: - internal admin dashboard - deployment guidance - QA/testing recommendations - anti-fraud / duplicate-referral logic Questions to Answer in Your Proposal Please answer the following: 1. Have you built a waitlist + referral + rewards backend before? 2. What stack would you recommend for this project and why? 3. How would you structure the database? 4. How would you prevent duplicate or fraudulent referral rewards? 5. What service would you use for automated welcome emails? 6. How would you track user location? 7. How would you structure this so it can later connect to the app? 8. Please share examples of similar work. 9. Please explain step by step how you would approach this build. Final Note This is an important pre-launch project for us. We are looking for a developer who can bring both technical execution and thoughtful system design to the table. If you have built similar systems and can demonstrate strong backend thinking, we would love to hear from you.