Firebase Expert for React Native Safety App

I need an experienced Firebase backend developer to assist with an existing React Native/Expo mobile safety application. The Firebase project and GitHub repository have already been created. The developer will work with my existing development team to review and implement: • Firebase Authentication and token validation • Firestore database architecture and collections • Firestore and Storage security rules • Cloud Functions using Node.js/TypeScript • Firebase App Check • Integration support for the React Native/Expo application • Testing, debugging, and technical documentation The application includes trip information, emergency contacts, safety check-ins, location-related features, alerts, and SOS functionality. Strong Firebase security experience is required. The developer must: • Have proven Firebase and React Native/Expo experience • Work through our GitHub repository using branches and pull requests • Collaborate with our team through Slack and video meetings • Provide written progress updates • Document all work and provide a recorded handoff • Never make production changes without approval Please provide examples of relevant Firebase projects and explain your experience with Firestore security rules, Cloud Functions, App Check, and React Native/Expo integration. I want to begin with a small paid architecture and security review. Additional implementation work will be divided into fixed-price milestones after the review.