Design Expedia.com

Problem Open-ended: design Expedia.com — a travel booking site covering search, pricing, and booking across hotels/flights/cars.

Functional requirements

• Destination/inventory search with filters and pricing; listing detail pages; booking with payment; user accounts with trip history.
• Scope with the interviewer (e.g. start with hotels only).

Non-functional requirements

• Read-heavy (search:booking well over 100:1); search p99 < 500 ms; no double-booking.
• Scale to discuss: tens of millions of users, thousands of search QPS, holiday-season spikes.

Areas to go deep

• Inventory freshness vs search speed.
• Double-booking prevention on the booking path.
• Caching per layer and inventory sync from suppliers.