lithos

https://github.com/main-path/lithos

lithos is a self-contained embedded key-value store written from scratch as a native extension — no external database dependency. It uses a log-structured merge (LSM) tree: a write-ahead log makes every write durable, an in-memory sorted memtable flushes to immutable SSTables (with bloom filters), and compaction merges them. Keys and values are arbitrary binary strings; keys are kept in sorted order so you get ordered iteration and range scans, plus crash recovery via WAL replay. Windows MSVC (mswin) Ruby only.