Open-source alternatives to MapDB

redb is an embedded key-value store and ACID-compliant storage engine. It functions as a persistent storage system for saving and retrieving data as key-value pairs within a tree structure. The engine is built as an MVCC transactional database, utilizing multi-version concurrency control to manage simultaneous reads and writes without blocking. It employs a single-writer multi-reader model to ensure data consistency while allowing multiple threads to access the store. The system provides persistent state management and atomic transaction management to prevent data corruption during crashes.

This project is a disk-backed key-value store and persistent data structure library for Python. It provides a mechanism for persisting mappings, sets, and queues to the local filesystem to bypass memory limitations and cache expensive function results across threads and processes. The system serves as a cross-process synchronization tool, offering distributed locks, semaphores, and barriers to coordinate shared resource access. It implements advanced caching strategies such as probabilistic stampede prevention, sharded data partitioning to increase throughput, and least-recently-used eviction

LiteDB is a serverless, embedded NoSQL document database for .NET applications. It persists data into a single portable file, functioning as a BSON data store that resides within the application process rather than running as a separate server. The system is ACID compliant, utilizing write-ahead logging to ensure atomic, consistent, isolated, and durable transactions. It includes built-in encryption to provide secure local data storage and protect files on disk from unauthorized access. The project covers object-document mapping to convert classes into document formats, indexed search capabi

Hazelcast is a distributed data platform that combines an in-memory data grid with a stream processing engine to support real-time analytics and event-driven applications. It functions as a partitioned, distributed key-value store that replicates data across cluster nodes to provide low-latency access and high availability. The platform also serves as a distributed SQL query engine, allowing users to execute standard SQL statements against both in-memory datasets and external data sources. What distinguishes Hazelcast is its use of a distributed consensus subsystem to maintain strongly consis

OpenTSDB is a distributed time series database and metrics engine designed for storing and managing massive volumes of high-cardinality system metrics. It functions as a data store and analytics platform that enables large-scale metric ingestion and infrastructure performance monitoring across a distributed cluster. The system distinguishes itself through a distributed storage abstraction that supports multiple backends such as HBase, Cassandra, and Google Bigtable. It utilizes a hierarchical metric tree to organize time series and employs numeric identifier indexing to reduce storage footpri

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

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

Kùzu is an embedded property graph database engine designed for high-performance analytical queries and local data management. It operates as a library within the host application process, utilizing a columnar-based storage architecture and just-in-time query compilation to execute complex graph traversals and pattern matching efficiently. By mapping database files directly into system memory, it ensures data durability and high-speed access while maintaining ACID-compliant transactional integrity. The engine distinguishes itself by integrating vector similarity search and full-text search di

ToyDB is a distributed SQL database that provides a system for storing and querying data across multiple nodes. It focuses on maintaining strong consistency and fault tolerance through the implementation of a distributed consensus algorithm. The project distinguishes itself by supporting historical data versioning, enabling time-travel queries to retrieve the state of the database from a specific point in the past. It utilizes multi-version concurrency control to manage ACID transactions and ensure data integrity during concurrent operations. The system covers relational data modeling with t

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

LMDB is an embedded key-value storage engine that provides ACID-compliant data persistence. It is a memory-mapped database that utilizes B+ trees to store key-value pairs, ensuring atomicity, consistency, isolation, and durability. The engine maps files directly into the virtual address space to minimize data copying and system calls. This approach enables high-performance local caching and low-latency data access, specifically optimizing for read-heavy database workflows. The system implements a transactional model with copy-on-write versioning and single-writer multi-reader locking. These

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

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

TypeDB is a strongly-typed graph database and knowledge graph management system. It serves as a multi-model data store that unifies relational, document, and graph structures into a single environment, functioning as both an ACID compliant database and a declarative query engine. The system distinguishes itself through the use of n-ary hypergraph modeling and polymorphic type hierarchies. It employs a strongly-typed schema to enforce structural rules and validate data integrity, allowing for type-based polymorphic inference and role-based interface polymorphism to resolve complex relationship

Couchbase Lite for iOS is an embedded NoSQL database engine designed for native mobile and desktop applications. It functions as a library within the application process, providing local document storage and structured querying capabilities that allow software to remain fully functional and responsive without an active internet connection. The library distinguishes itself through a replication engine that synchronizes local database changes with a central server to maintain consistent state across multiple devices. This synchronization process utilizes a delta-based protocol to transmit only

This project is an open source relational database management system and SQL database designed for storing and managing structured data. It functions as a relational database for ensuring consistency and reliability, while also operating as a vector database for storing and querying high-dimensional vector embeddings. The system incorporates a columnar storage engine to optimize analytical query processing and large-scale data aggregation. It further enables vector similarity search, allowing users to find similar items by querying vector embeddings. The software covers a broad capability su

LiteDB is a serverless NoSQL document store and embedded database engine for .NET applications. It persists unstructured documents and binary data into a single standalone disk file, allowing the database to run within the application process rather than as a separate server. The system supports strongly typed queries through Language Integrated Query and allows the execution of standard SQL commands for data retrieval and transformation. It provides native mapping of plain classes into document formats and secures stored information via symmetric-key file encryption. The engine includes cap

This project is a curated collection of academic papers, books, and technical resources designed for studying the architecture and implementation of database management systems. It serves as a comprehensive educational guide for engineers and researchers looking to understand the fundamental principles behind modern data storage and retrieval. The repository distinguishes itself by providing structured learning paths across critical database domains, including the design of persistent storage engines, the mechanics of query optimization, and the complexities of distributed transaction managem

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

Neo4j is a native graph database management system designed to store and query highly connected data using a property-graph model. It provides an ACID-compliant transaction engine that ensures data integrity, supported by a distributed cluster architecture that maintains causal consistency across nodes. Users interact with the system through a declarative query language, which allows for complex pattern matching and path traversal without requiring manual traversal logic. The platform distinguishes itself through its hybrid approach to data retrieval, combining traditional graph-based queries

Realm-Cocoa is a NoSQL mobile database engine and reactive object database designed for local data storage on mobile devices. It serves as a non-relational alternative to Core Data and SQLite, storing data as objects rather than tables. The system functions as an encrypted local store that protects sensitive application data using encryption. It provides reactive data synchronization, allowing application objects and user interfaces to update automatically when the underlying database changes.

CouchDB is a NoSQL document database that stores data as flexible documents and exposes a RESTful API for data management over HTTP. It functions as a distributed document store, synchronizing and replicating data across multiple nodes to ensure high availability and consistency. The system includes a full-text search engine that transforms database records into queryable documents, supporting sorting and pagination. Data synchronization is handled via multi-master replication, which exchanges revision histories to maintain consistency across distributed nodes. The database utilizes multi-ve

This is a mobile object database and NoSQL local data store that replaces relational tables with a schema-based model. It functions as a reactive data store, using live object observations and change notifications to trigger automatic user interface refreshes. The system provides built-in mobile cloud data synchronization to keep local datasets consistent with a remote server across multiple devices. It also includes security features for encrypted local storage, protecting sensitive on-disk data using at-rest encryption keys and fine-grained access control. Broad capabilities include object

Realm Java is a NoSQL mobile object database and reactive database engine. It provides a persistent local data store that saves native objects directly to disk, replacing traditional SQL storage and object-relational mapping layers. The system functions as a real-time data synchronizer, coordinating local database changes with a cloud backend across multiple devices. It integrates a reactive engine that uses change listeners and asynchronous event streams to automatically update user interfaces when underlying data changes. The project covers object-oriented data modeling, CRUD operations, a

Ledisdb is a high-performance NoSQL database server written in Go. It functions as a key-value store that supports complex data structures and utilizes persistent disk storage to manage data volumes that exceed system memory capacity. The system is designed as both a standalone server and an embeddable engine library that integrates directly into Go binaries. It features a scriptable data store that executes server-side Lua scripts for atomic operations and provides an HTTP API for data exchange using JSON, BSON, and msgpack serialization. The database includes capabilities for distributed d

WCDB is a cross-platform storage layer and embedded database engine that serves as a framework for SQLite. It functions as an object relational mapper, linking application classes to database tables to enable data operations via objects rather than raw queries. The project is distinguished by an integrated encryption layer for securing data at rest and a full-text search engine that uses language-specific tokenizers for text lookups. It also features transparent field compression to reduce storage footprints and a connection-pooling model to coordinate simultaneous read and write operations a

Badger is an embeddable key-value store written in Go that provides persistent data storage for byte keys and values. It is a persistent database that utilizes a tiered LSM tree storage model to optimize disk storage and retrieval efficiency. The system features an ACID transaction engine that ensures data integrity through serializable snapshot isolation and multi-version concurrency control. It also provides an encrypted key-value store with data-at-rest encryption and a managed encrypted key registry to secure stored information. The engine covers a broad set of capabilities including hig