Complete Two-Sided Marketplace Backend

Looking for a developer to complete an already-prototyped two-sided marketplace. The project has an existing web frontend built with HTML/CSS/JS, and we need someone to build the backend using Node.js and Express.js. The ideal candidate will have experience in creating RESTful APIs and integrating payment systems. This is a part-time role with a project scale of small and a duration of less than one month probably. Looking for a developer to complete an already-prototyped two-sided marketplace (existing web frontend, built with HTML/CSS/JS). I need someone to build out the backend and make everything fully functional and production-ready. What's needed: Firebase backend: authentication, Firestore database, security rules, Cloud Functions Two distinct user profile types (provider / customer) with separate dashboards Real-time chat between users Appointment booking system with calendar and availability management Stripe integration: recurring monthly subscription + automatic charge per single transaction (pay-per-action model) Push and email notifications (automated) Onboarding questionnaire with automatic matching logic between the two user types Verified reviews system (post-interaction) Mobile-responsive design throughout Requirements: Everything must run fully automated — no manual intervention needed after launch (signups, payments, matching, bookings, notifications) Clean, secure, well-documented code Experience with Firebase + Stripe integrations is a strong plus Budget: open to proposals in the €3.000-4.500 range depending on experience and timeline