Why it matters

B-trees are DB + filesystem workhorses. Understanding shapes storage.

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The architecture

Node holds many keys + children.

Branching factor B: 100-1000+.

Height very small.

B-tree structureNodemany keysBranching Bwide fan-outHeightlog_B(N)Height 3-4 for billions of keys; matches disk block size for locality
B-tree.
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How it works end to end

Node size = disk block.

Fewer disk reads.

Insertions split nodes.

Deletions merge or borrow.