Shopping Cart Backend

Cart Scenarios

Guest: Redis session with 30-day TTL
Registered: Redis + PostgreSQL persistence
Merge on login: combine guest + account carts

Scale

• p99 < 50ms for cart operations
• 100K concurrent users
• Cart size limit: 100 items

Key Points

• Understanding Shopping Cart Backend is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes

Cart Data (Redis)

{
  "cart:user:123": {
    "items": [{"productId": 100, "price": 89.99, "quantity": 1}],
    "total": 89.99
  }
}

Cart Merging on Login

1. Load guest cart from Redis
2. Load user cart from database
3. Merge items (add quantities for duplicates)
4. Save merged cart
5. Delete guest cart

Key Points

• Understanding Shopping Cart Backend is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes

Cleanup Strategy

• Cron job: hourly, archive carts > 30 days
• Abandoned cart: reminder at 24hrs, archive at 7 days

Optimizations

• Redis hash for O(1) operations
• Lazy total recalculation
• 30-day TTL, refresh on activity

Key Points

• Understanding Shopping Cart Backend is essential for production systems
• Always consider scalability and maintainability
• Test thoroughly before deploying to production
• Monitor performance and set up alerting

Common Patterns

1. Validation: Always validate input at the boundary
2. Error Handling: Use structured error responses
3. Logging: Log key events for debugging
4. Testing: Unit, integration, and load tests
5. Documentation: Keep docs updated with code changes