Flipkart / Shopping site — Simple

Problem statement (interviewer prompt)

Design Flipkart's storefront and order pipeline for the Indian market: handle Big-Billion-Day flash sales (10× normal load), UPI + COD + cards + EMI payments, hot-deal stampede protection (waiting rooms), and tight integration with an in-house logistics network.

flowchart LR
  U([User])
  CAT[Catalog]
  CART[Cart]
  ORD[Order]
  PAY[Payment]
  LOG[Logistics]
  WHS[Warehouse]
  U --> CAT
  U --> CART --> ORD --> PAY
  ORD --> LOG --> 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,CART,ORD,PAY,LOG service;
    class WHS datastore;