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E-commerce Backend

Design product catalog, cart, and checkout for an e-commerce platform.

2h
0 problems
Topic Progress0%

Requirements & Scope

Functional Requirements

  1. Product Catalog - Browse, search, filter products
  2. Shopping Cart - Add/remove items, persist across sessions
  3. Checkout - Address, payment, order placement
  4. Order Management - Track orders, status updates
  5. Inventory - Real-time stock tracking

Non-Functional Requirements

Metric Target
Throughput 10K orders/sec
Latency p99 < 200ms
Availability 99.99%

Scale Estimates

  • 1M daily active users
  • 100K products
  • 50K orders/hour peak

Architecture

Service Architecture

  • Product Service: PostgreSQL + Elasticsearch
  • Cart Service: Redis (session store)
  • Order Service: PostgreSQL + Kafka

Checkout Flow (Saga Pattern)

  1. Validate cart items and inventory
  2. Reserve stock (with timeout)
  3. Process payment
  4. Create order
  5. Clear cart
  6. Send confirmation

Each step is a saga participant with compensating actions.

Inventory Management

Use SELECT FOR UPDATE to prevent overselling:

BEGIN;
SELECT * FROM variants WHERE id = ? FOR UPDATE;
UPDATE variants SET reserved_quantity = reserved_quantity + 1
WHERE id = ? AND (stock_quantity - reserved_quantity) > 0;
COMMIT;

Database Design

Core Tables

  • products(id, name, category_id, base_price)
  • variants(id, product_id, sku, attributes JSONB, price, stock)
  • orders(id, user_id, status, items JSONB, total)

Key Design Decisions

  • JSONB for dynamic product attributes
  • GIN index for full-text search
  • Row-level locking for inventory
  • Elasticsearch for product search

Key Points

  • Understanding E-commerce 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

API Design

Endpoints

  • GET /api/products?category=shoes&minPrice=50
  • GET /api/products/{id}
  • POST /api/cart/items
  • PUT /api/cart/items/{id}
  • DELETE /api/cart/items/{id}
  • POST /api/checkout
  • GET /api/orders/{id}

Key Points

  • Understanding E-commerce 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

Practice Problems

0/3solved
Implement E-commerce Backend

Design and implement a solution for E-commerce Backend in a backend system. Consider scalability, error handling, and production readiness.

Solution
// E-commerce Backend implementation
// Key aspects: validation, error handling, logging, testing

public class EcommerceBackend {
    // Production-ready implementation
}
E-commerce Backend Edge Cases

Identify and handle edge cases for E-commerce Backend. What happens under high load, with invalid input, or during failures?

Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
E-commerce Backend Testing Strategy

Write a testing strategy for E-commerce Backend. Include unit tests, integration tests, and performance tests.

Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. How to prevent overselling in checkout?

Question 1 options

2. Which pattern handles checkout steps with rollback?

Question 2 options

3. What is the primary purpose of E-commerce Backend?

Question 3 options

4. What is a common mistake when implementing E-commerce Backend?

Question 4 options

Flashcards

Question

How to prevent overselling?

Click to reveal answer

Answer

SELECT FOR UPDATE + stock check in transaction

Question

Checkout uses which pattern?

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Answer

Saga pattern for distributed transactions

Question

What is E-commerce Backend?

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Answer

E-commerce Backend is a key concept in backend development.

Question

When to use E-commerce Backend?

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Answer

Use E-commerce Backend when building production systems that require reliability, scalability, and maintainability.

Question

E-commerce Backend best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1.Product search needs Elasticsearch
  • 2.Cart uses Redis for sessions
  • 3.Checkout uses saga pattern
  • 4.Inventory requires row-level locking

Interview Tips

  • •Start with high-level architecture
  • •Discuss consistency vs availability

Cheat Sheet

E-commerce Backend

  • Product: PostgreSQL + Elasticsearch
  • Cart: Redis (session store)
  • Orders: PostgreSQL + Kafka
  • Checkout: Saga pattern
  • Inventory: SELECT FOR UPDATE