Senior React Native Architect & Mentor (Firebase) - Part-Time / Flexible Hours

Project Overview: We are a fast-moving startup building a dynamic, real-time service marketplace mobile app. Our MVP launches in 5 months and features complex workflows, including real-time geolocation, secure AI integrations, and a split-payment ecosystem. Our current team consists of an Agile Tech Lead and two dedicated Junior Full-Stack Developers handling the daily coding. We are looking for a Fractional Senior Mobile Architect (Part-Time) to act as our "Code Guardian" and technical brain. Your Role (You will NOT be coding screens 40 hrs/week): This is a strategic, high-level role. We need your expertise to design the system architecture, secure our serverless backend, and ensure our Junior developers write clean, scalable code through rigorous Pull Request (PR) reviews. Tech Stack: Frontend Mobile: React Native, Expo (Managed Workflow), TypeScript (Strict). Backend / Cloud: Firebase (Authentication, Cloud Firestore, Cloud Functions). Core Integrations: Stripe Connect / Mercado Pago (Split Payments), AI APIs (OpenAI/Gemini), Native Geolocation. Key Responsibilities: Data Architecture: Model scalable NoSQL Firestore collections optimized for low latency and cost-effective read/write operations. Serverless Security: Design Firebase Cloud Functions to act as a secure bridge for our AI integrations and payment gateways, ensuring APIs are never exposed on the client side. Code Review & Mentorship: Asynchronously review, comment, and approve PRs from our Junior developers. You will enforce best practices and catch architectural red flags. State Management: Define the global state management strategy (e.g., Zustand) and local caching rules. The Ideal Candidate: Proven track record deploying complex React Native apps to the App Store/Play Store. Absolute mastery of Firebase (especially Firestore Security Rules and NoSQL modeling). Previous experience integrating multi-party payment gateways (Marketplace flows). Exceptional asynchronous communicator (leaving clear, educational comments on GitHub/GitLab). Working Dynamics: Hours: Part-time, flexible schedule (estimated 5-15 hours/week depending on the sprint). Style: 100% remote, asynchronous via Agile/Scrum. No micromanagement. We pay for your technical judgment and mentorship, not just keyboard time. To Apply: Please start your proposal with the word "GUARDIAN" so we know you read the description. Briefly mention a similar React Native + Firebase architecture you've reviewed or built recently.