Berkeley DB C AGPLv3 or Proprietary B-Tree, Hash Berkeley DB (BDB) is a software library that provides a high-performance embedded database for key/value data. Tokyo/Kyoto Cabinet C++ GPLv2.1 / GPLv3 w/ compatibility exceptions B-Tree, Hash Tokyo Cabinet and Kyoto Cabinet are two libraries of routines for managing key-value databases. SQLite C Public Domain B-Tree, LSM SQLite is a relational database management system contained in a C programming library. UnQLite C 2-Clause BSD (Simplified) Hash UnQLite is a in-process software library which implements a self-contained, serverless, zero-configuration, transactional NoSQL database engine. LevelDB C++ 3-Clause BSD (New/Revised) LSM LevelDB is an open source on-disk key-value store written by Google. LevelDB by Basho C++ 3-Clause BSD (New/Revised) LSM A fork of LevelDB modified to benefit the Riak environment. LevelDB by HyperDex C++ 3-Clause BSD (New/Revised) LSM A fork of LevelDB intended to meet the needs of HyperDex while remaining compatible with LevelDB. RocksDB C++ Apache v2 or GPLv2 LSM RocksDB is an embeddable persistent key-value store for fast storage from Facebook. (LevelDB by Facebook) Sophia C 2-Clause BSD (Simplified) Sophia Sophia is an advanced transactional MVCC key-value/row storage library. WiredTiger C GPLv2 or GPLv3 B-Tree, LSM WiredTiger is a high performance, scalable, production quality, NoSQL, Open Source extensible platform for data management. Percona/TokuFT C++ GPLv2 or AGPLv3 Fractal Tree PerconaFT is a high-performance, transactional key-value store. ForestDB C++ Apache v2 HB+-Trie Forestdb - A Fast Key-Value Storage Engine Based on Hierarchical B+-Tree Trie. Sparkey C Apache v2 Hash Simple constant key/value storage library, for read-heavy systems with infrequent large bulk inserts. MDBM C 3-Clause BSD (New/Revised) Hash MDBM is a fast memory-mapped DBM clone by Yahoo. LMDB C OpenLDAPv2.8 (BSD-style) B-Tree Lightning Memory-Mapped Database (LMDB) is a software library that provides a high-performance embedded transactional database in the form of a key-value store. MDBX C OpenLDAPv2.8 (BSD-style) B-Tree Modified version of LMDB (Symas Lightning Memory-Mapped Database) NessDB C "BSD" Buffered-Tree A very fast transactional key-value, embedded database storage engine. Vedis C Sleepycat (GPL-style) or Proprietary Hash Vedis is an embeddable datastore C library built with over 70 commands similar in concept to Redis but without the networking layer. Rlite C 2-Clause BSD (Simplified) Hash Self-contained, serverless, zero-configuration, transactional Redis-compatible database engine. SkipDB C 3-Clause BSD (New/Revised) Skip List Small, portable, ACID, C implemented BDB style database based on skiplists instead of b-trees. EJDB C LGPLv2.1 B-Tree, Hash Embedded JSON Database engine C library. UpscaleDB C Apache v2.0 B-Tree A very fast lightweight embedded database engine with built-in analytic functions. Eblob C LGPLv3 Eblob is an append-only low-level IO library, which saves data in blob files. WhiteDB C GPLv3 or Proprietary or Royalty Free w/ Conditions Hash WhiteDB is a lightweight NoSQL database library written in C, operating fully in main memory. Beringei C++ 3-Clause BSD (New/Revised) TimeSeries Beringei is a high performance, in-memory storage engine for time series data. IOWOW C MIT Skip List The C11 persistent key/value storage engine library based on skip list data structure.