LSM Tree

Definitions

1. Log-Structured Merge Tree — a data structure optimized for write-heavy workloads. Writes go to an in-memory buffer (memtable), then flush to sorted, immutable on-disk files (SSTables) that are periodically merged (compacted). Trades read performance for write throughput. Used by RocksDB, LevelDB, Cassandra, ScyllaDB, and ClickHouse.

   In plain English: A data structure that makes writes super fast by buffering them in memory and periodically sorting them to disk.

   Example: "Cassandra uses LSM trees — writes are always append-only so it handles 100K writes/sec, but reads may check multiple SSTables."

Related Terms

• Array
• Binary Tree
• Cell Array
• Collections
• Consistency
• Record
• Skip List
• B+ Tree