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Design Flight Booking and Voting Systems

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MediumSoftware EngineerOnsiteSystem Design

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This question evaluates system design competencies including large-scale backend architecture, data modeling and indexing, database internals, concurrency control to prevent overselling, and high-throughput real-time streaming and metrics for live updates.

Answer both system design prompts.

Part A: Flight Ticket Booking System

Design the backend for a flight ticket booking product. The system should support searching flights, selecting an itinerary, booking tickets for passengers, and preventing overselling.

Cover the following:

  • Data model for entities such as Flight, Passenger, and FlightTicket or Booking.
  • Indexes to build and why.
  • How B-tree indexes work internally and how that affects query design.
  • End-to-end user experience flow and the backend queries for booking a flight.
  • How to avoid double booking when many users try to buy the same flight or seat concurrently.

Part B: Real-Time High-QPS Voting System

Design a real-time voting system for a fast-food promotion during a major live event. Users can quickly tap to vote for a taco flavor and should see a live results board.

Requirements:

  • Traffic may reach a few million votes per second for a short burst.
  • The vote action should have low latency.
  • The results board should update in near real time.
  • The design should be reliable under sudden traffic spikes.

Cover the following:

  • APIs, services, storage, and data flow.
  • How to use Kafka or another durable streaming system.
  • How to model real-time counters and time-series metrics.
  • Relevant Kafka internals and time-series database internals.
  • Deployment strategy on Kubernetes or EKS, including autoscaling.