Eleven Writes for One: LSM Trees as a Data Structure

Deep End Era. Engineering with Sankalp · Oct 28, 2026 · 55m

At two in the morning in a Leeds mill, storage engineer Imogen Hart sees eleven bytes hitting disk for every byte her delivery vans send. In part one of The Deep End's Data Structures series we build the LSM tree from the 1991 O'Neil, Cheng, Gawlick and O'Neil idea onward: a post room with an in-tray, a day book and a patient archivist. We follow a write and a read by ear, do levelled and tiered compaction maths aloud, see why bloom filters make LSM point reads competitive, revisit Discord's tombstones stuck at 99.9999 percent, and fix Imogen's write amplification by changing key shape rather…