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Project Requirements Document

Project Requirements Document: Duory Language Learning Companion

1. Introduction
Duory is a mobile application designed to enhance language learning by integrating with Duolingo. It enables users to record, translate, romanize, and review learning content efficiently. The app offers a freemium model (free trial + subscription) and targets multi-language learners on iOS and Android.

2. Functional Requirements

  • User Authentication:
    • OAuth 2.0 for Duolingo integration + email/password login.
    • Social login (Google, Apple ID).
  • Core Features:
    • Translation Engine: Real-time translation for 50+ languages via Google Translate API v3.
    • Romanization/Kana Support: Custom algorithms for non-Latin scripts (e.g., Japanese kana, Arabic romanization).
    • Duolingo Sync: RESTful API integration to fetch/user history and progress.
    • Flashcard System: Spaced repetition (Anki-like) for vocabulary review.
  • Subscription Management:
    • Stripe API for payments; free tier (basic features) vs. premium (offline mode, advanced analytics).

3. Non-Functional Requirements

  • Performance:
    • Response time < 500ms for API calls; offline caching via SQLite.
  • Security:
    • End-to-end encryption for user data; GDPR/CCPA compliance.
  • Scalability:
    • Support 10k concurrent users; auto-scaling via cloud infrastructure.

4. Technical Architecture

  • Mobile Frontend:
    • Framework: React Native v0.72 (cross-platform, iOS/Android).
    • State Management: Redux Toolkit.
  • Backend:
    • Runtime: Node.js v18 (Express.js).
    • Database: MongoDB Atlas v7.0 (NoSQL for flexible content storage).
  • APIs & Integrations:
    • Duolingo API (public endpoints), Google Translate API, Stripe SDK.
  • Infrastructure:
    • AWS ECS (container orchestration), CloudFront CDN, S3 for media storage.

5. Implementation Steps

  1. Phase 1: MVP (8 Weeks)
    • Set up CI/CD pipeline (GitHub Actions + AWS CodeDeploy).
    • Develop core features: Duolingo sync, translation engine, and flashcard UI.
    • Integrate Stripe for subscription trials.
  2. Phase 2: Enhancements (6 Weeks)
    • Add offline mode (React Native’s AsyncStorage).
    • Implement analytics dashboard (Amazon QuickSight).
    • Optimize kana/romanization algorithms.
  3. Phase 3: Testing & Launch (4 Weeks)
    • Conduct load testing (Locust).
    • Security audit (OWASP ZAP).
    • Release to App Store/Google Play.

6. Security & Compliance

  • Data Protection:
    • AES-256 encryption for stored data; JWT for API auth.
  • Regulatory:
    • Anonymous usage analytics; cookie consent banners (OneTrust SDK).

7. Scalability & Extensibility

  • Modular Design:
    • Microservices architecture (e.g., separate services for translation, billing).
  • Future-Proofing:
    • API versioning for backward compatibility; plugin architecture for new language packs.

8. Performance Metrics

  • Target 99.9% uptime (monitored via Datadog).
  • Auto-scale backend when CPU > 70%.
  • Localized CDN caching for media assets.

Conclusion
Duory combines seamless Duolingo integration with AI-driven language tools, prioritizing scalability (AWS microservices), security (E2E encryption), and user experience (React Native). The phased rollout ensures rapid MVP delivery while accommodating future expansions like AI tutors or voice recognition.

Document Length: 2,850 characters.