Amazon — Notes

Functional

• Browse catalog, search, recommendations.
• Cart, checkout, multiple addresses & payment methods.
• Order placement → inventory hold → payment → fulfillment.
• Returns, RMAs, refunds.
• Reviews, ratings, Q&A.
• Marketplace (3rd-party sellers), FBA.

Non-functional

• p99 product page < 300 ms.
• 99.99% checkout availability.
• Read:Write 100:1 for catalog; 10:1 for cart.
• Strong consistency for orders + payments; eventual OK for catalog and views.

Capacity (rough)

• 200+ M items, 1B+ users, 100k+ orders/min peak (Prime Day).
• Catalog reads: millions/s.
• Catalog storage: TB; with images many PB.

Schema highlights

• products(id, title, price, attrs, seller_id, category)
• inventory(sku, warehouse, on_hand, reserved)
• carts(user_id, [items])
• orders(id, user_id, items[], status, totals, payment_id)
• payments(id, order_id, status, amount, provider_ref, idempotency_key)

Trade-offs

• Microservices (1000s) enable team autonomy but require strong contracts.
• Saga over 2PC for order flow.
• Multi-warehouse inventory for latency / cost; complicates allocation.
• Read replicas for catalog, but check stock at commit.

Refs

• Amazon engineering talks (DynamoDB origin, SOA papers), Werner Vogels blog.
• "Building Mission-Critical Financial Services Apps" re:Invent.
• ByteByteGo "Design Amazon", Alex Xu Vol 2.