Amazon — Simple

Problem statement (interviewer prompt)

Design Amazon's core retail flow: browse a massive catalogue, add to cart, checkout, place an order, deduct inventory, charge payment, and fulfil from a warehouse. Handle 100k+ orders/min at peak (Prime Day) with strong consistency on payment + inventory.

flowchart LR
  U([User])
  CAT[Catalog]
  SRCH[Search]
  CART[Cart]
  ORD[Order]
  PAY[Payment]
  INV[Inventory]
  WHS[Warehouse / Fulfillment]
  U --> CAT
  U --> SRCH
  U --> CART --> ORD --> PAY
  ORD --> INV --> WHS

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class U client;
    class CAT,SRCH,CART,ORD,PAY,INV service;
    class WHS datastore;