Design Travel Booking Platform (Expedia/Booking.com) - Frontend System Design Interview Guide
Design a production-ready travel booking platform like Expedia, Booking.com, or Kayak with flight/hotel search, multi-step booking flows, real-time pricing, and payment integration.
Backend as Black Box: Assume you have APIs for search, pricing, and booking. Focus on the frontend architecture.
Key Challenges
This problem explores complex e-commerce flows:
- Multi-Step Booking Wizard: Search → Select → Details → Payment → Confirmation
- Real-time Pricing: Dynamic prices that change during booking
- Session & Cart Management: Hold inventory, handle timeouts
- Form Orchestration: Complex validation across multiple steps
- Payment Integration: Secure checkout, error handling
When users book travel, they expect smooth multi-step flows, accurate pricing, and reliable payment processing—even as prices change in real-time. This solution designs a travel booking platform that handles multi-step wizards, real-time pricing, session management, and payment integration while gracefully managing price volatility. The key insight: a good booking platform re-validates prices at confirmation time, handles session timeouts gracefully, and preserves state across refreshes.
HLD interview focus: Requirements, architecture, tradeoffs, data flow, and scaling decisions. Any implementation snippets shown are optional unless explicitly asked.
Key Takeaways
- ✓Use URL-based step navigation for back button and bookmarks
- ✓Model booking flow as state machine for valid transitions
- ✓Session storage provides resilience across page refreshes
- ✓Pre-payment price verification prevents checkout surprises
- ✓Session timer creates urgency with clear countdown
- ✓Progressive form validation gives real-time feedback
- ✓Error recovery should preserve user progress when possible
- ✓Mobile-first forms with proper input types and touch targets