System Design: Online Bookstore (Browse + Purchase)

Context

Design an online bookstore that allows customers to browse/search books, view product details, add to cart, and purchase. Assume web and mobile clients, users can be guests or logged-in, and third-party payment processing is used. Optimize for high read traffic on catalog/search and correctness during checkout.

Requirements

Functional Requirements

1. Catalog and discovery
   • Browse categories, filter, sort (by price, rating, relevance).
   • Full-text search with facets (author, genre, format, price range, language).
   • Product detail page: title, authors, description, ISBN, formats (hardcover/ebook), price, availability, images, ratings.
2. Cart and checkout
   • Cart operations: create, add/update/remove items, view cart, merge guest cart on login.
   • Checkout: shipping options, taxes, discounts/coupons, payment, order confirmation.
   • Order history for users; guest order lookup by email+order ID.
3. Inventory and pricing
   • Real-time inventory/availability per SKU (format/edition/warehouse).
   • Promotions/discounts; price snapshots at order time.
4. Payments
   • Integrate with a PSP; support cards and wallets; handle 3DS/SCA when applicable.
5. Notifications
   • Email confirmations for order placement, payment, and shipment.

Non-Functional Requirements

• Scale read-heavy catalog/search; low-latency PDP and cart.
• Strong consistency for inventory reservation and order state transitions.
• High availability (multi-AZ; consider multi-region DR).
• Security and privacy (PII, PCI scope minimization).
• Observability with actionable SLOs.
• Idempotent APIs for checkout/payment/order creation.

Deliverables

• APIs: search/browse, product detail, cart, checkout, payments, order history.
• Data model: books, authors, inventory, pricing, users, carts, orders.
• Service decomposition and storage choices (SQL/NoSQL), search indexing, caching/CDN, read/write patterns.
• Address inventory reservation and consistency, idempotency, security/privacy, observability, capacity planning, scalability/availability/fault tolerance.