Design a search query autocomplete system

Quick Overview

This question evaluates a candidate's ability to design a real-time, low-latency search autocomplete system, exercising competencies in architecture, indexing and serving, ranking and personalization, typo-tolerance, multilingual support, abuse prevention and privacy-aware data handling; it is categorized under System Design and emphasizes practical application with architectural-level conceptual reasoning. It is commonly asked to assess how candidates balance stringent latency and scalability requirements with personalization and trending signals, robustness to input errors and multiple languages, and metrics-driven trade-offs across caching, ranking and monitoring.

Design a search query autocomplete system

Company: OpenAI

Role: Machine Learning Engineer

Category: System Design

Difficulty: hard

Interview Round: Onsite

## Question Design a search autocomplete system that suggests completions as the user types. ## Requirements - Sub-100ms latency per keystroke. - Suggestions should be personalized and reflect trending queries. - Must handle typos and multiple languages. - Support abuse prevention (spam, offensive queries) and privacy constraints. ## Deliverables Architecture (data collection, indexing, serving), ranking strategy, caching, and evaluation metrics.

Quick Answer: This question evaluates a candidate's ability to design a real-time, low-latency search autocomplete system, exercising competencies in architecture, indexing and serving, ranking and personalization, typo-tolerance, multilingual support, abuse prevention and privacy-aware data handling; it is categorized under System Design and emphasizes practical application with architectural-level conceptual reasoning. It is commonly asked to assess how candidates balance stringent latency and scalability requirements with personalization and trending signals, robustness to input errors and multiple languages, and metrics-driven trade-offs across caching, ranking and monitoring.

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Dec 15, 2025, 12:00 AM
hardMachine Learning EngineerOnsiteSystem Design
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Question

Design a search autocomplete system that suggests completions as the user types.

Requirements

  • Sub-100ms latency per keystroke.
  • Suggestions should be personalized and reflect trending queries.
  • Must handle typos and multiple languages.
  • Support abuse prevention (spam, offensive queries) and privacy constraints.

Deliverables

Architecture (data collection, indexing, serving), ranking strategy, caching, and evaluation metrics.

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