Design Google Search
Last Updated: December 31, 2025
A web search engine is a system that crawls the internet, indexes web pages, and returns relevant results in response to user queries. It enables users to find information across billions of web pages in milliseconds.
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The core challenge is scale. The web contains hundreds of billions of pages, users expect results in under 500 milliseconds, and the content is constantly changing. A search engine must continuously discover new pages, understand their content, determine their importance, and serve relevant results to millions of concurrent users.
Popular Examples: Google Search, Bing, DuckDuckGo, Baidu, Yandex
What makes this problem fascinating from a system design perspective is its breadth. It is arguably one of the most comprehensive system design problems you can encounter.
Building a search engine touches on nearly every area of distributed systems: web crawling at massive scale, distributed storage for petabytes of data, information retrieval algorithms, machine learning for ranking, and low-latency serving infrastructure.
In this chapter, we will explore the high-level design of a web search engine like Google Search.
Let's start by clarifying the requirements: