Open-source alternatives to Lmdb

NutsDB is an ACID-compliant, embedded transactional storage engine that functions as both a disk-backed key-value store and an in-memory data structure store. It provides atomic and serializable transactions with commit and rollback capabilities to ensure strict data consistency for applications requiring a lightweight persistence layer. The engine distinguishes itself by supporting a variety of complex data types, including lists, sets, and sorted sets, alongside standard byte-slice storage. It implements a transactional storage model featuring hot backups and a compaction algorithm to maint

bbolt is an ACID-compliant embedded key-value store for Go applications. It persists all data in a single memory-mapped file on disk, organizing information using B+ trees to facilitate sorted key iteration and efficient range queries. The project distinguishes itself through a hierarchical data organization model, allowing buckets to be nested within other buckets to create a tree-like structure. It employs a single-writer, multi-reader locking mechanism and copy-on-write transactions to ensure serializable isolation and data integrity. The system includes comprehensive data management capa

MapDB is an embedded database engine and disk-backed collection library that stores Java collections on disk or off-heap. It functions as a local data processing engine designed to handle datasets that exceed available physical RAM. The project utilizes off-heap data storage to eliminate garbage collection overhead and employs disk overflow caching to balance memory and disk usage. It provides specialized utilities for filtering and analyzing large volumes of local data on a single machine. The system ensures data integrity through ACID-compliant transactions and multi-version concurrency co

Datascript is an immutable, in-memory state store and schema-based triple store. It manages application state as a versioned database, storing data as immutable facts consisting of an entity, attribute, value, and transaction. The project provides a logic engine for executing Datalog queries with support for implicit joins, recursive rules, and negation. It also features a declarative pull API for retrieving deeply nested entity graphs and related data structures. The database enforces data integrity through schema-driven constraints and attribute types. It supports atomic transactions, plug

RoseDB is an embedded key-value database and log-structured storage engine. It functions as a library-based database that runs within an application process to provide local data persistence without the need for a separate database server. The project implements a Bitcask-style store, utilizing an append-only log format to maximize write throughput and minimize seek time. It ensures data consistency by grouping multiple read and write operations into single atomic units. The storage architecture relies on an in-memory key index for constant-time lookups and uses segment-based file management

Sled is an embedded key-value store and ACID-compliant database designed for high-performance data persistence. It functions as a log-structured storage engine that organizes data using B+ trees to support efficient range queries and prefix scans. The engine implements a zero-copy data store model, utilizing epoch-based reclamation to provide direct references to cached values without memory allocations. It distinguishes itself through a combination of write-ahead logging, page cache optimizations to reduce write amplification on flash storage, and serializable transactions for atomic multi-k

goleveldb is an embedded key-value storage database for Go. It provides local data persistence and indexing, allowing applications to store and retrieve information using unique keys without requiring a separate server. The database organizes data using a log-structured merge-tree and persistent indexing in lexicographical order. This structure supports efficient range scans and prefix-based searches. The system includes capabilities for atomic batch writes to ensure data consistency and avoid partial updates. Performance is managed through write-ahead logging, memory-based buffering, and bl

etcd is a distributed, strongly consistent key-value store designed to provide reliable storage for critical system metadata and coordination primitives. It functions as a distributed consensus engine, utilizing a replicated log and leader-based state machine to ensure that all nodes in a cluster maintain a synchronized view of data. By providing atomic operations and linearizable reads and writes, it serves as a foundational component for distributed systems requiring high availability and fault tolerance. The system distinguishes itself through its multi-version concurrency control, which e

NeDB is a JavaScript embedded NoSQL document store designed for Node.js and the browser. It functions as an in-memory data store with the option to persist documents to a local file system, ensuring data survives application restarts. The project utilizes a MongoDB-compatible API to perform data operations, allowing it to serve as a lightweight document indexing system and a persistent file database without requiring a separate database server. Capabilities include querying, inserting, updating, and deleting documents, as well as the ability to create indexes on specific fields to accelerate

Hiredis is a minimalistic C client library designed to send commands and receive responses from Redis servers using a binary-safe protocol. It functions as a core toolkit providing a Redis protocol parser, a secure connector, and both synchronous and asynchronous driver interfaces. The library distinguishes itself through a decoupled protocol parser that converts raw byte streams into structured data objects independently of the network transport layer. It supports high-performance pipelining to batch multiple commands into a single network round-trip and provides a secure networking layer fo

FoundationDB is an ACID-compliant distributed transactional key-value store. It functions as a scalable database engine that ensures strict serializability and data consistency across a cluster of servers using a shared-nothing architecture. The system is distinguished by its multi-region replication capabilities, allowing data to be synchronized across different datacenters for high availability and disaster recovery. It utilizes optimistic concurrency control to manage distributed transactions and employs a majority-based coordination system to maintain cluster state. The platform provides

Chronicle Queue is a high-performance data handling system featuring off-heap message queues, memory-mapped file stores, and replicated message stores. It provides a binary compatible memory layout that enables different programming languages to share data without serialization overhead. The system utilizes a replicated message store to synchronize data across multiple nodes, ensuring high availability and instant failover. Its memory-mapped architecture supports deterministic replay from disk and low-latency data recording. The project implements off-heap memory management and zero-allocati

FastImageCache is an iOS image caching library that provides a persistent disk-based image store. It utilizes a persistent bitmap cache to store images in uncompressed formats and incorporates an image pre-processing pipeline to optimize assets before they are committed to storage. The library optimizes rendering performance by using memory-mapped image tables for constant-time retrieval and byte-aligned data layouts to prevent memory copies. It organizes images of identical dimensions into shared tables and manages disk space through a least-recently-used cache eviction system. The project

PalDB is an embeddable key-value storage engine for Java designed for high-performance data retrieval. It functions as a library that persists data into a single, immutable binary file, providing a storage solution for write-once workloads that require minimal memory overhead compared to standard in-memory collections. The system distinguishes itself through a write-once data layout that eliminates the need for locking mechanisms during concurrent read operations. By utilizing memory-mapped file access and sorted key indexing, the engine enables rapid lookups directly within the process addre

RoseDB is a persistent key-value database and log-structured storage engine. It functions as a lightweight storage system that utilizes a log-structured hash table and a Bitcask engine implementation to provide fast data retrieval and disk-backed persistence. The system operates as an atomic transaction engine, grouping multiple read and write operations into single units to maintain data consistency. It handles data through a key-value model that supports individual insertions, lookups, and deletions. The database provides capabilities for batch data processing and atomic updates. Additiona

This is an in-memory B-Tree data structure implementation for Go. It provides a memory-resident collection that maintains sorted elements to enable efficient retrieval, modification, and the management of sorted key-value maps. The project supports ordered mutable collections and sorted key-value stores, allowing for fast lookups, insertions, and deletions while preserving the sort order of keys. It provides capabilities for range searching within sorted memory structures and maintains the organization of datasets through self-balancing node splitting and recursive binary search.

Mini-LSM is an educational storage engine and key-value database library designed to demonstrate the implementation of log-structured merge-tree architecture. It serves as a pedagogical resource for understanding how to build high-performance storage systems from the ground up, focusing on the mechanics of persistent data structures and disk-based storage. The project provides a functional framework for managing data through memory-to-disk flushing and multi-version concurrency control. It distinguishes itself by implementing snapshot-based isolation, which allows for consistent views of the

Lance is a versioned columnar data format and storage engine designed as a multimodal AI lakehouse. It serves as a vector database storage engine and a cloud object store dataset manager, organizing images, video, audio, and embeddings into a unified format optimized for machine learning workflows. The project distinguishes itself by combining a columnar layout for structured data with a specialized blob store for large multimodal tensors. It implements a hybrid search engine that integrates vector similarity search, full-text search, and SQL analytics on a single dataset, supported by a stor

This library provides a collection of specialized data structures for the Swift language that extend the standard library with advanced container types. It includes implementations for double-ended queues using ring-buffers, priority queues based on min-max heaps, and memory-efficient bit-set and bit-array storage for boolean values. The project features ordered collections that maintain elements in sorted order via B-tree implementations, as well as persistent sets and dictionaries that use compressed prefix trees to share data between mutated copies. It also provides specialized containers

SlateDB is a cloud-native key-value store and distributed database engine that utilizes a log-structured merge-tree architecture. It serves as a transactional storage layer designed to persist data directly to cloud object storage. The engine differentiates itself by optimizing read performance for remote storage through the use of bloom filters and multi-level block caching. It employs a single-writer multi-reader model and provides the ability to create zero-copy clones via copy-on-write checkpointing. The system supports atomic transactions, range queries, and snapshot-based concurrency c

This project is an educational implementation of a relational database engine written in C. It functions as a SQLite clone, demonstrating the internal mechanics of a database system through a C-based systems project that focuses on manual memory management and file I/O. The engine is distinguished by its use of a bytecode virtual machine, which executes database operations by compiling SQL statements into low-level instructions. It utilizes a B-tree database engine to organize records in a balanced tree structure, ensuring efficient insertion, search, and range scanning. The system covers co

Pebble is an embedded key-value storage engine written in Go, designed as a library that provides durable, write-optimized data persistence directly within applications. It organizes data using a log-structured merge-tree (LSM-tree) structure, where writes are first buffered in an in-memory skiplist memtable and persisted to a write-ahead log before being flushed to block-based SSTable files on disk. The engine supports atomic batch commits, configurable write synchronization, and automatic background compaction that merges and rewrites sorted runs to reclaim space and maintain read performanc

MiniOB is an open-source educational relational database kernel designed for learning the internals of database systems. It implements a dual-engine storage architecture combining B+ Tree and LSM-Tree, supports SQL parsing and query execution, and provides transactional processing with multi-version concurrency control. The system communicates with clients using the MySQL wire protocol and includes a vector database extension for storing and querying high-dimensional vectors. The project distinguishes itself through its comprehensive coverage of core database concepts in a single, learnable c

CloudCompare is a professional software application for processing and analyzing 3D point clouds and polygonal meshes. It functions as a 3D mesh analysis tool and a large dataset visualizer designed to display and manage millions of points in a 3D environment. The software provides specialized capabilities for point cloud comparison, utilizing an optimized octree structure to calculate spatial differences between two 3D datasets. This allows for the identification of variations and errors between point clouds or between a point cloud and a mesh. The system covers broad 3D data analysis areas

H2 is a JDBC-compliant relational database management system written in Java. It functions as an embeddable SQL database that can run directly within an application process to remove network latency, or as an in-memory database for high-performance volatile storage. It also includes a web-based console for executing SQL commands and administering schemas. The system is characterized by its flexible deployment modes, including a standalone server mode for remote TCP/IP access and a mixed mode for simultaneous local and remote connectivity. It features a dialect emulation layer and compatibilit

This is an educational relational database engine used in Carnegie Mellon University's database systems course. Students learn internals by implementing core components of a working database, including storage, indexing, concurrency control, and crash recovery. The system covers key database architecture: a B+ tree index for fast key-based lookups and range scans, a disk-oriented buffer pool that caches pages from disk, an iterator-based query execution model that composes physical operators, page-based storage for records, two-phase locking for coordinating concurrent transactions, and write

ObjectBox Java is an embedded NoSQL object database for Java and Android that stores data objects directly without relational mapping. It functions as a native-process storage engine, allowing applications to persist plain Java or Kotlin classes as entities. The project distinguishes itself with an on-device vector database capability, utilizing HNSW indexes to perform approximate nearest neighbor searches and semantic similarity queries. It also includes a locally hosted web-based browser for visualizing data objects, schemas, and dependency diagrams. The database covers a broad range of da