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Intermediate Topic 20 of 52 Data Structures

B-Trees

Wide balanced trees optimized for disk block access.

How it works

A B-tree node holds many sorted keys and many children, which keeps the tree shallow and wide. All leaves are at the same depth, and nodes split when full and merge when too empty, so the tree stays balanced automatically. Choosing a node size equal to a disk page lets one disk read fetch hundreds of keys, so lookups need only a handful of I/O operations.

Where it is used

Database indexes, file systems such as NTFS, ext4 and Btrfs, and key-value stores use B-trees to search huge datasets stored on disk. They support range scans efficiently.

Common pitfall

Node splits and merges are intricate, and concurrent updates need careful locking or latch protocols. Random inserts cause page fragmentation, and write amplification can be high on SSDs. Choose the order based on page size and key size.

Where it fits in the course

B-Trees is topic 20 of 52 in Data Structures, rated Intermediate. It follows Red-Black Trees. The next topic is B+ Trees.

Practice and explore

How to study this topic

  1. Read the explanation above and restate the definition in your own words.
  2. Open the interactive lesson and answer its mini quiz.
  3. Read the common pitfall, then write a short example that avoids it.
  4. Check your understanding in the Data Structures quiz, and revisit the topic if you miss a question.

Frequently asked questions

What is B-Trees?
Wide balanced trees optimized for disk block access. It belongs to Data Structures and is an intermediate-level topic.
Where do people use B-Trees?
Database indexes, file systems such as NTFS, ext4 and Btrfs, and key-value stores use B-trees to search huge datasets stored on disk.
What is the most common mistake with B-Trees?
Node splits and merges are intricate, and concurrent updates need careful locking or latch protocols.
What should I learn before this topic?
Start with Red-Black Trees, the topic just before it in Data Structures.
How can I practice it?
Answer the mini quiz in the interactive lesson, then take the Data Structures quiz. You can also explore Binary Search Tree in the Visual Lab.
Is B-Trees hard to learn?
It is an Intermediate topic. Be comfortable with the Beginner topics in this area first, then read the common pitfall carefully, since it is where most mistakes happen.
How long does it take to learn B-Trees?
Most learners can read the explanation and finish the interactive lesson in under an hour. Fluency comes from applying the idea, so plan a few short practice sessions with the quiz.
Which topics are related to B-Trees?
Red-Black Trees, B+ Trees, AVL Trees are closely connected. The full list is in the related topics section of this page.
What should I study after B-Trees?
Continue with B+ Trees, the next topic in Data Structures.

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