PHP Interview Questions for Walmart

1. How is PHP used in large-scale e-commerce platforms like Walmart?
PHP handles backend APIs, user sessions, order processing, product management, and integrates with payment gateways and inventory systems.

2. How do you optimize PHP applications for high-traffic websites?

  • Implement caching using Redis or Memcached.
  • Use load balancers and horizontal scaling.
  • Optimize SQL queries and enable OPcache.

3. How do you manage product catalogs efficiently in PHP?

  • Use pagination with LIMIT and OFFSET.
  • Cache frequently accessed product data.
  • Implement search indexing with ElasticSearch.

4. How do you handle real-time inventory updates?

  • Use WebSockets or AJAX polling for updates.
  • Implement database transactions for consistency.

5. How do you prevent overselling of products?

  • Lock inventory records during purchase transactions.
  • Validate stock availability before order confirmation.

6. How do you calculate discounts and promotions dynamically?

  • Store discount rules in the database.
  • Apply business logic during checkout based on user eligibility.

7. How do you implement flash sales without crashing the system?

  • Use distributed locking (e.g., Redis Redlock).
  • Queue purchase requests and process them asynchronously.

8. How do you handle abandoned carts in PHP?

  • Track user cart sessions.
  • Send automated reminders using scheduled scripts.

9. How do you manage large file uploads for product images?

  • Validate file types and sizes.
  • Store files in cloud storage (e.g., AWS S3).
  • Use background processing for image resizing.

10. How do you calculate shipping costs dynamically?

  • Integrate with third-party shipping APIs.
  • Calculate based on weight, dimensions, and distance.

11. How do you implement user wishlists?

  • Create a wishlist table linked to user accounts.
  • Allow adding/removing items with simple AJAX calls.

12. How do you prevent duplicate orders during network failures?

  • Implement idempotency keys.
  • Validate order status before processing payments.

13. How do you manage multi-currency pricing in PHP?

  • Store product prices in a base currency.
  • Convert using real-time exchange rates at checkout.

14. How do you handle product recommendations?

  • Use collaborative filtering algorithms.
  • Store user activity and suggest products based on purchase history.

15. How do you prevent fraudulent transactions?

  • Implement CAPTCHA during checkout.
  • Integrate fraud detection APIs.
  • Validate IP addresses and payment methods.

16. How do you implement order tracking in PHP?

  • Update order status at each stage (processing, shipped, delivered).
  • Expose tracking APIs for the frontend.

17. How do you manage product reviews and ratings?

  • Allow verified buyers to leave reviews.
  • Use moderation workflows to approve or reject reviews.

18. How do you optimize search functionality in an e-commerce store?

  • Implement search indexing using ElasticSearch.
  • Provide filters for categories, brands, and price ranges.

19. How do you securely integrate payment gateways like PayPal or Stripe?

  • Use SDKs or APIs provided by the payment gateway.
  • Never store card details; rely on tokenization.

20. How do you handle promotional coupon codes?

  • Store coupons in a database with usage limits and expiration dates.
  • Validate coupons at checkout.

21. How do you calculate taxes dynamically based on location?

  • Integrate with tax calculation APIs like Avalara.
  • Apply tax rates based on the user’s shipping address.

22. How do you prevent inventory inconsistencies during high demand?

  • Use database transactions and locking mechanisms.
  • Validate stock levels before processing the order.

23. How do you handle session management in a scalable way?

  • Store sessions in Redis or Memcached.
  • Use secure cookies and regenerate session IDs after login.

24. How do you implement product image optimization?

  • Generate multiple image sizes for different devices.
  • Use lazy loading for faster page loads.

25. How do you monitor API performance and availability?

  • Implement health check endpoints.
  • Use monitoring tools like New Relic or Datadog.

26. How do you manage cart data for guest users?

  • Store cart data in sessions or cookies.
  • Merge guest cart with user cart upon login.

27. How do you handle refunds programmatically?

  • Integrate refund APIs from payment gateways.
  • Update order and refund status in the database.

28. How do you implement referral programs?

  • Track referrals using unique codes.
  • Apply discounts or rewards when successful referrals are completed.

29. How do you prevent bots from buying limited stock items?

  • Implement CAPTCHA and purchase limits per user.
  • Use device fingerprinting and behavioral analytics.

30. How do you generate invoices in PHP?

  • Use libraries like Dompdf or TCPDF to create PDF invoices.
  • Send invoices automatically via email after order confirmation.

31. How do you handle product returns and exchanges?

  • Provide an interface for return/exchange requests.
  • Update inventory and order status accordingly.

32. How do you prevent duplicate user accounts?

  • Enforce unique email addresses or mobile numbers during registration.
  • Validate accounts using email/SMS verification.

33. How do you handle large-scale promotional campaigns?

  • Cache promotional data to reduce database load.
  • Use background jobs to schedule and activate campaigns.

34. How do you implement location-based product availability?

  • Store product availability by warehouse locations.
  • Display products based on user’s selected delivery location.

35. How do you ensure password policies meet security standards?

  • Enforce minimum password length and character types.
  • Use password_hash() for secure password storage.

36. How do you implement loyalty points in an e-commerce system?

  • Store points earned per transaction.
  • Allow users to redeem points during checkout.

37. How do you prevent data breaches in e-commerce portals?

  • Enforce strong password policies.
  • Secure APIs with proper authentication and authorization.
  • Regularly audit and patch vulnerabilities.

38. How do you manage discount stacking restrictions?

  • Implement business logic to allow only one type of discount per order.

39. How do you ensure fast product page loading?

  • Use caching for static content.
  • Optimize images and implement lazy loading.
  • Minimize database queries on product pages.

40. How do you handle customer support ticket management in PHP?

  • Create a support ticket module linked to user accounts.
  • Provide ticket status updates and escalation mechanisms.

41. How do you implement personalized marketing emails?

  • Store user activity data and preferences.
  • Use email services like SendGrid to send personalized offers.

42. How do you calculate cart totals with taxes and discounts?

$total = $subtotal - $discount + $tax;

43. How do you handle marketplace vendor commissions?

  • Track sales per vendor.
  • Calculate commissions automatically and generate payout reports.

44. How do you integrate with shipping providers like FedEx or DHL?

  • Use their REST APIs to calculate shipping costs and generate tracking numbers.

45. How do you ensure smooth checkout processes for users?

  • Keep checkout steps minimal.
  • Provide multiple payment options.
  • Save frequently used addresses for quicker access.

46. How do you implement product bundling offers?

  • Create special bundle products in the catalog.
  • Apply bundle pricing automatically during checkout.

47. How do you handle order cancellations and automatic stock updates?

  • Update inventory quantities immediately after cancellation.
  • Notify warehouse systems of changes.

48. How do you implement split payments (multiple payment methods in one transaction)?

  • Allow partial payments using different payment methods.
  • Track remaining balances and payment statuses accurately.

49. How do you secure coupon codes from being misused?

  • Assign usage limits and expiration dates.
  • Restrict usage to specific user accounts or categories.

50. How do you handle multi-warehouse inventory management?

  • Track inventory per warehouse.
  • Assign fulfillment locations based on delivery proximity and stock availability.