core practice · coding problem
B-tree page split
Page holds 4 keys, insert 5th triggers split. After split how many keys in each page (order 5)?
The mechanism
A B-tree is a wide, shallow tree sized to disk pages: each node holds many keys so the tree stays ~3-4 levels deep even for billions of rows. Reads are fast and in-place; writes do random page updates.
Expected evidence
2 keys in left, 2 in right, median promoted.
Try this drill in the practice workspace →
Hints when you need them
- Split keeps tree balanced.
- Fanout controls height.
Watch for these mistakes
- Confusing B-tree (in-place, read-optimized) with LSM (append, write-optimized)
- Ignoring page splits and write amplification
- Forgetting that B-trees keep keys sorted, enabling range scans