Indexing Strategies: B-Trees, Hash Tables, and R-Trees

Issue #24 of "System Design Interview Roadmap" - Part II: Data Storage

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The Hidden Architecture Behind Every Query

Last week, I was debugging a performance issue for a client whose search functionality had slowed to a crawl. Their database had grown from thousands to millions of records, and what once took milliseconds now took seconds. The culprit? Missing indexes. It reminded me how easy it is to take these fundamental data structures for granted until they become your bottleneck.

Why Indexing Matters

Imagine searching for a name in a 1,000-page phone book without an alphabetical index. You'd have to scan every page—an O(n) operation. This is precisely what happens in a database full table scan. Indexes are the difference between your query returning in 3ms ve…