Tech Abstractions
ML System Design·Easy

Design a Search Ranking System

Asked at Google, Elastic, Algolia

Design a search ranking system for an e-commerce platform's product search. When a user types a query like "wireless noise cancelling headphones under $200," the system must return the most relevant products ranked by relevance, with considerations for business metrics like conversion rate.

Scale

  • 50 million products in the catalog
  • 10 million search queries per day
  • Target latency: under 200ms for search results page
  • Catalog updates: 100K product changes per hour (new products, price changes, inventory updates)

Design Requirements

  1. Design the overall search pipeline from query to ranked results.
  2. Explain your approach to query understanding — handling synonyms, misspellings, and intent.
  3. Design the ranking model — what features and what architecture?
  4. Describe how you measure search quality and run experiments.
  5. Discuss how to balance relevance with business objectives (promoting high-margin products).

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