# Technology Stack Decisions

**Last Updated**: 2026-02-14

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## Decisions Made

### 1. Rust Web Framework: Axum
**Decision**: Axum 0.7.x

**Rationale**:
- Superior I/O performance for encrypted data transfer
- Better streaming support for large encrypted responses
- Lower memory usage for concurrent connections
- Tower middleware ecosystem
- Excellent async patterns for lazy loading

**Reference**: [2026-02-14-performance-findings.md](./2026-02-14-performance-findings.md)

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### 2. Mobile Framework: React Native
**Decision**: React Native 0.73+ for iOS + Android

**Platform Strategy**:
- **Primary**: Mobile apps (iOS + Android) - Daily health tracking, sensor integration
- **Secondary**: Web browser - Extensive reporting, visualization, profile management

**Rationale**:
- **70-80% code sharing** between mobile and web (single language: TypeScript)
- **Health sensor integration**: react-native-health (HealthKit), react-native-google-fit (Health Connect)
- **QR code scanning**: react-native-camera
- **Encryption**: react-native-quick-crypto (AES-256-GCM, PBKDF2)
- **Web charts**: Recharts for React (beautiful visualizations)
- **Team skills**: Single language (JavaScript/TypeScript) reduces development cost
- **Time to market**: Faster than native or Flutter

**Reference**: [2026-02-14-frontend-mobile-research.md](./2026-02-14-frontend-mobile-research.md)

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### 3. Web Framework: React
**Decision**: React 18+ for web companion app

**Rationale**:
- **70-80% code sharing** with React Native (business logic, state, API, encryption)
- **Charts**: Recharts for beautiful health data visualizations
- **Ecosystem**: Largest npm ecosystem
- **Team skills**: Single language (TypeScript)

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## Technology Stack Summary

### Backend
- **Framework**: Axum 0.7.x
- **Runtime**: Tokio 1.x
- **Middleware**: Tower, Tower-HTTP
- **Database**: MongoDB (with zero-knowledge encryption)
- **Language**: Rust

### Mobile (iOS + Android)
- **Framework**: React Native 0.73+
- **Language**: TypeScript
- **Health Sensors**: react-native-health, react-native-google-fit
- **Encryption**: react-native-quick-crypto
- **HTTP**: Axios

### Web
- **Framework**: React 18+
- **Language**: TypeScript
- **Charts**: Recharts
- **HTTP**: Axios

### Shared (Monorepo)
- **Language**: TypeScript
- **State**: Redux/Zustand (TBD)
- **API**: Axios
- **Encryption**: AES-256-GCM, PBKDF2
- **Validation**: Zod
- **Date**: date-fns

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## Still To Be Decided

### 1. State Management (Priority: High)

**Options**:
- Redux (mature, large ecosystem)
- Zustand (simple, modern)
- Jotai (atomic, minimal)

**Considerations for Normogen**:
- 70-80% code sharing between mobile and web
- Complex state (family structure, multi-person profiles)
- Offline synchronization
- Encrypted data caching

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### 2. Authentication Strategy (Priority: High)

**Options**:
- JWT (stateless, scalable)
- Session-based (traditional, easier revocation)
- Passkey/WebAuthn (passwordless, modern)

**Considerations for Normogen**:
- Zero-knowledge password recovery
- Token revocation strategy
- Multi-factor authentication (future)
- Integration with client-side encryption keys
- Family member access control

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### 3. Database Schema (Priority: High)

**Collections to Design**:
- Users (authentication, profiles)
- Families (family structure)
- Health Data (encrypted health records)
- Lab Results (encrypted lab data)
- Medications (encrypted medication data)
- Appointments (encrypted appointment data)
- Shared Links (time-limited access tokens)

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## Recommended Order

1. Rust Framework: Axum (COMPLETED)
2. Mobile/Web Framework: React Native + React (COMPLETED)
3. State Management: Redux vs Zustand
4. Authentication: JWT with recovery phrase
5. Database Schema: Design MongoDB collections
6. Create POC: Health sensor integration test
7. Implement Core Features: Authentication, encryption, CRUD

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## Next Research Priority

**Research Question**: Which state management library (Redux vs Zustand) is best for Normogen's encrypted health data platform?

**Considerations**:
- 70-80% code sharing between React Native and React
- Complex state (family structure, multi-person profiles)
- Offline synchronization
- Encrypted data caching
- TypeScript support
- Bundle size (mobile)

**Estimated Research Time**: 1-2 hours