LSM tree.

also: LSM trees · log-structured merge tree · LSM-tree · SSTable · SSTables · memtable

A write-optimised structure: writes go to an in-memory table, flush to sorted immutable files, and background compaction merges them.

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Write path: WAL, then the in-memory memtable; when full it is flushed as a sorted SSTable.
Reads check the memtable, then SSTables newest first; Bloom filters skip files without the key.
Compaction merges files and drops overwritten and deleted data.
Used by RocksDB, LevelDB, Cassandra and HBase: great write throughput, more read work.

also: LSM trees · log-structured merge tree · LSM-tree · SSTable · SSTables · memtable

A write-optimised structure: writes go to an in-memory table, flush to sorted immutable files, and background compaction merges them.

Write path: WAL, then the in-memory memtable; when full it is flushed as a sorted SSTable.
Reads check the memtable, then SSTables newest first; Bloom filters skip files without the key.
Compaction merges files and drops overwritten and deleted data.
Used by RocksDB, LevelDB, Cassandra and HBase: great write throughput, more read work.