Worklog Week 3

Week 3 Objectives: Sprint 1 - Backend Foundation (Part 1)

• Implement Authentication with Amazon Cognito
• Build Domain Layer (Entities)
• Implement Repository Layer with DynamoDB
• Create Lambda handlers for Auth endpoints
• Setup API Gateway with Cognito authorizer

Weekly Tasks:

Week 3 Results:

1. Authentication System:

• ✅ Cognito User Pool configured with email/password + Google OAuth
• ✅ Signup flow working: email verification, password validation
• ✅ Login flow returns ID token, access token, refresh token
• ✅ Token refresh mechanism working

2. Domain Layer:

• ✅ 4 core entities implemented with full validation
• ✅ Value objects for type safety
• ✅ Domain exceptions for error handling
• ✅ Unit tests coverage > 90%

3. Repository Layer:

• ✅ Abstract repository interfaces defined
• ✅ DynamoDB implementation with single-table design
• ✅ CRUD operations working correctly
• ✅ Error handling and retry logic

4. Use Cases:

• ✅ Auth use cases implemented with business logic
• ✅ Input validation and sanitization
• ✅ Proper error handling
• ✅ Unit tests with mocked repositories

5. API Endpoints:

• ✅ 3 auth endpoints deployed and working:
  • POST /auth/signup - User registration
  • POST /auth/login - User login
  • POST /auth/refresh - Token refresh
• ✅ Cognito authorizer protecting endpoints
• ✅ CORS configured correctly
• ✅ Integration tests passing

Code Structure:

src/
├── domain/
│   ├── entities/
│   │   ├── user.py
│   │   ├── flashcard.py
│   │   ├── session.py
│   │   └── scenario.py
│   ├── value_objects/
│   │   ├── email.py
│   │   └── user_id.py
│   └── exceptions.py
├── use_cases/
│   └── auth/
│       ├── signup_user.py
│       ├── login_user.py
│       └── refresh_token.py
├── repositories/
│   ├── user_repository.py (interface)
│   └── ...
├── infrastructure/
│   ├── dynamodb/
│   │   ├── user_repository_impl.py
│   │   └── connection.py
│   └── cognito/
│       └── auth_service.py
└── handlers/
    └── auth/
        ├── signup.py
        ├── login.py
        └── refresh.py

Testing Results:

Unit Tests:

• ✅ Domain entities: 25 tests, 100% pass
• ✅ Use cases: 18 tests, 100% pass
• ✅ Repositories: 15 tests, 100% pass
• Total: 58 unit tests, 0 failures

Integration Tests:

• ✅ Signup flow: Email verification working
• ✅ Login flow: Tokens returned correctly
• ✅ Protected endpoints: Authorizer working
• ✅ Error cases: Proper error responses

Challenges and Solutions:

Challenge 1: Cognito token validation in Lambda

• Solution: Use python-jose library to verify JWT tokens

Challenge 2: DynamoDB conditional writes for duplicate prevention

• Solution: Use ConditionExpression with attribute_not_exists

Challenge 3: Lambda cold start slowing down first request

• Solution: Optimize imports, lazy loading for heavy libraries

Challenge 4: Type hints with Python dynamic typing

• Solution: Use mypy strict mode, Pydantic for validation

Challenge 5: Encountered some errors during first deployment

• Solution: Debug step by step, reference documentation and ask mentor when needed

Next Week Plan (Sprint 1 - Week 4):

• Implement Profile management (GET/PUT /profile)
• Implement Flashcard CRUD operations
• Setup frontend project with Next.js
• Create basic UI components
• Integrate frontend with Auth APIs
• Attend regular team meetings to review progress