Difficulty: Intermediate
Reading Time: 25 min read
Last Updated: September 01, 2025
🌳 B+ Trees — The Gold Standard of Database Indexing
When you run:
SELECT * FROM Products WHERE price BETWEEN 50 AND 150;
…the difference between that query taking milliseconds or minutes often comes down to one structure: the B+ tree.
Most developers learn about arrays, linked lists, and binary search trees early on. But in the real world of databases and filesystems, these structures fall short. They’re too linear, too shallow, or too memory-focused. Disk access is slow — and disk I/O is the bottleneck every serious database has to solve.
That’s where the B+ tree comes in.
Unlike simple binary search trees, the B+ tree:
- Keeps itself perfectly balanced, no matter how many records you insert or delete.
- Stores multiple keys per node, aligned with disk block sizes, to minimize expensive I/O.
- Places all actual data in the leaf nodes, while internal nodes act only as guides.
- Links those leaves together, making range queries blazingly fast with just a single pass.
This design means operations scale logarithmically (O(log n)), even across billions of records. It’s why relational databases like MySQL, PostgreSQL, and SQLite, and filesystems like NTFS, XFS, HFS+, all rely on B+ trees under the hood.
But the brilliance of B+ trees isn’t just in raw performance. It’s in the elegance of the design:
- 🌲 Binary Search Trees gave us ordering but crumbled under imbalance.
- 🌲 AVL & Red-Black Trees introduced balance, but only suited for in-memory data.
- 🌲 B-Trees adapted to disk, but mixed data and routing.
- 🌲 B+ Trees perfected the model: separating routing from data, linking leaves, and unlocking massive scalability.
So the next time you fire off a query and marvel at how instantly your results appear, remember: it’s a humble B+ tree making it happen, silently keeping the system in balance.
Read the full article in my Notion blog here:
- 🔗 Read it on Notion
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The full article lives in my Notion blog here, which serves as the single hub for all my articles and ensures consistent formatting across platforms. You can read this article directly in the Notion link above. Feel free to share your thoughts or feedback in the site comments—or drop me a note on LinkedIn.
About the Author
Abdul-Hai Mohamed | Software Engineering Geek’s.
Writes in-depth articles about Software Engineering and architecture.
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