Design a system to find the cheapest flight tickets across multiple providers. Support search by origin, destination, dates (including flexible ranges), cabin class, and number of stops. Describe the high-level architecture (ingestion/aggregators, normalization, deduplication, search index), APIs, caching, data freshness and update propagation, rate limiting and retries, consistency vs availability trade-offs, and strategies for scalability and cost control. Specify schemas and indexes that enable fast queries and price updates.

This question evaluates a candidate's proficiency in system design, distributed backend architecture, data modeling, real-time provider integration, and operational concerns for building a scalable, cost-efficient flight price search service.

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Design flight-price search service | Circle Interview Question

System Design: Cheapest Flight Search Across Multiple Providers

Context

Design a backend system that searches multiple flight providers (airlines, OTAs, GDS/aggregators) to return the cheapest flight tickets for users. The system must handle a high volume of queries, volatile prices, and frequent updates while remaining scalable and cost-efficient.

Requirements

Inputs: origin, destination, departure date(s), return date(s), cabin class, number of stops.
Date flexibility: exact dates or flexible windows (e.g., ±3 days) and calendar view.
Core outputs: list of itineraries/offers sorted by price with filters, plus a fast “cheapest per day” calendar.
System concerns to describe:
1. High-level architecture: ingestion from providers, normalization, deduplication, search index.
2. APIs: search, quote/validate (re-price), and ancillary endpoints.
3. Caching strategy.
4. Data freshness and update propagation.
5. Rate limiting, retries, and resilience patterns.
6. Consistency vs availability trade-offs.
7. Scalability and cost-control strategies.
8. Schemas and indexes that enable fast queries and rapid price updates.

Requirements

Inputs: origin, destination, departure date(s), return date(s), cabin class, number of stops.

Date flexibility: exact dates or flexible windows (e.g., ±3 days) and calendar view.

Core outputs: list of itineraries/offers sorted by price with filters, plus a fast “cheapest per day” calendar.

System concerns to describe:

High-level architecture: ingestion from providers, normalization, deduplication, search index.
APIs: search, quote/validate (re-price), and ancillary endpoints.
Caching strategy.
Data freshness and update propagation.
Rate limiting, retries, and resilience patterns.
Consistency vs availability trade-offs.
Scalability and cost-control strategies.
Schemas and indexes that enable fast queries and rapid price updates.

Design flight-price search service

Quick Overview

System Design: Cheapest Flight Search Across Multiple Providers

Context

Requirements

Solution

Submit Your Answer to Earn 20XP

Design flight-price search service

Quick Overview

System Design: Cheapest Flight Search Across Multiple Providers

Context

Requirements

Solution

Submit Your Answer to Earn 20XP