Databases for Embedded / in-process

The in-process SQL engine that ships in every phone, browser and OS: one file, zero servers.

In-process columnar SQL database: the SQLite of analytics, running inside your app or notebook.

Meta's embeddable LSM-tree key-value engine, the storage layer under dozens of databases.

Desktop database and forms builder bundled with Microsoft 365; still everywhere in back offices.

Meta's C++/Python library for fast dense-vector similarity search and clustering, CPU and GPU.

Tiny memory-mapped B+tree with ACID transactions and lock-free readers; reached 1.0 in 2026.

The Java search library at the heart of Elasticsearch, OpenSearch and Solr, now with HNSW vectors.

Real PostgreSQL compiled to WebAssembly: an embeddable Postgres for browsers, Node, Bun and Deno.

Google's original small, fast LSM key-value library, now in limited-maintenance mode.

Lightweight, MVCC relational database from the InterBase lineage, embeddable or client-server.

Extensible Rust query engine library on Apache Arrow for building databases and data systems.

The browser's built-in transactional object store, and the storage layer under most web local-first libraries.

Dependency-free SQLite extension for vector search that runs anywhere SQLite does, including WASM.

Turso's open-contribution SQLite fork with native vectors, a network server and embedded replicas.

Early Java multi-model database mixing documents, graphs and objects, now in patch-only mode.

Embedded, serverless retrieval database on the Lance columnar format for multimodal AI data.

The most popular IndexedDB wrapper, with live queries and an optional Dexie Cloud sync service.

Ground-up Rust rewrite of SQLite with concurrent writes, async I/O, CDC and vector search.

Fast pure-Java SQL engine for embedded, in-memory and test databases, with compatibility modes.

Sync engine that keeps on-device SQLite in sync with Postgres, MongoDB, MySQL or SQL Server.

JavaScript database for browsers and Node that speaks the CouchDB replication protocol.

Single-header C++ HNSW library with SIMD distance kernels and bindings for a dozen languages.

Transparent persistence for Python objects with ACID transactions and history.

Lucene-inspired full-text search library in Rust, the engine under Quickwit and ParadeDB.

Self-tuning embeddable SQL database with MobiLink sync, still shipped inside ISV apps but frozen at v17.

Pure-Python document store that keeps every table in one human-readable JSON file.

Embedded, in-process OLAP engine powered by ClickHouse, used mainly from Python.

Community-maintained continuation of Kùzu: embedded columnar graph database with Cypher.

MongoDB's default storage engine: MVCC B-tree with compression and snapshot isolation.

Pure-JavaScript in-memory SQL engine for browsers and Node.js that queries arrays, JSON, CSV and Excel files.

Reactive local-first NoSQL database for JavaScript with pluggable storage and replication.

Embedded LSM storage engine that writes straight to object storage like S3.

In-memory JavaScript document store with indexes and pluggable persistence; no longer maintained.

Tiny type-safe local JSON database for Node, Electron and the browser using plain JavaScript.

Apache Jena's native RDF store, embeddable in Java or served over SPARQL with Fuseki.

Tiny reactive in-memory store for tables and values, with persisters and CRDT sync.

Embarcadero's small-footprint SQL database for servers and embedded apps, with built-in AES encryption.

Mature C++ probabilistic full-text search library with bindings for a dozen languages.

Lazy-loading reactive database for React Native and React apps, built on SQLite.

The standard embedded JVM cache, with heap, off-heap and disk tiers and optional Terracotta clustering.

SQLite with transparent 256-bit AES encryption of the whole database file.

The 1990s-era embedded key-value library, now Oracle-owned, AGPL-licensed and rarely updated.

Header-only C++ HNSW library with Python bindings, from the authors of the HNSW algorithm.

Log-structured, embeddable key-value engine in pure Rust with keyspaces and transactions.

Classic 1985 desktop relational database with Query by Example; now a frozen extra in WordPerfect Office.

Spotify's memory-mapped random-projection-tree ANN library; stable but no longer evolving.

Small, fast SPARQL database in Rust that embeds in Rust, Python and JavaScript or runs as a server.

Immutable in-memory database with Datomic-style Datalog queries for Clojure, ClojureScript and JavaScript.

Tiny in-memory JavaScript collection library with SQL-like filtering for the browser and Node.js.

Embedded Datalog database blending relational, graph and vector queries; dormant since 2024.

Local-first TypeScript platform: SQLite on each device, end-to-end encrypted sync through relays.

Pure-Rust embedded key-value store: copy-on-write B-trees, ACID, and a stable file format.

Young C storage-engine library: transactional LSM with MVCC, column families and TTL.

Ambitious lock-free embedded Rust database whose 1.0 rewrite has stalled in alpha.

French integrated database and app-development platform for desktop, client/server and web apps.

Fast on-device object database with built-in HNSW vector search and an optional commercial sync server.

Pure-Go full-text, geo and vector indexing library from Couchbase.

The Btrieve/Pervasive lineage: zero-admin embedded database with key-level and SQL access, now edge-focused.

etcd's maintained fork of BoltDB: a simple, pure-Go B+tree store in a single file.

Serverless single-file NoSQL document database for .NET, in the spirit of SQLite.

Pure-Go LSM key-value store that separates keys from values to cut write amplification.

Eclipse Foundation's Java RDF framework with native, LMDB and in-memory SPARQL stores.

Managed SQLite-compatible cloud for database-per-tenant apps, with embedded replicas and offline sync.

Long-running pure-Java SQL database with strong SQL:2023 coverage, used embedded and in LibreOffice.

Commercial object database for Java that implements JPA and JDO natively, with no ORM layer.

Lightweight pure-Dart key-value store for Flutter; development continues in the Hive CE fork.

Off-heap, memory-mapped key-value store for Java with microsecond latency and cross-process sharing.

Swedish standards-strict SQL engine built for embedded, automotive and real-time systems.

Canonical's embeddable C library that makes SQLite highly available with Raft replication.

Embedded JSON document database with SQL++ queries, vector search and sync to Couchbase.

Embedded Java database exposing concurrent Maps, Sets and Queues backed by disk or off-heap memory.

Desktop database born on the Commodore 64 in 1983, still sold as Superbase NG with the SIMPOL language.

Tencent's mmap-backed key-value store for mobile apps, built as a faster SharedPreferences/NSUserDefaults.

Google Research's ANN library using anisotropic quantization; the tech behind Vertex AI and AlloyDB vectors.

Embeddable bitemporal database that keeps every revision of JSON and XML resources queryable.

Open-source, durable Datalog database for Clojure with Datomic-style immutable history.

Cockroach Labs' Go LSM engine, inspired by RocksDB and tuned for CockroachDB.

Heavily reworked LMDB descendant: memory-mapped ACID B+tree with auto-growing files.

Low-latency in-memory plus on-disk SQL database with HotStandby failover, sold today by UNICOM.

Embeddable JSON document database in C, with a JQL query language and optional HTTP/WebSocket server.

Rust graph database, inspired by Facebook's TAO, usable as an embedded library or a gRPC server.

Pioneering C++/Java object database that maps persistent objects into virtual memory; now sold by IgniteTech.

Windows desktop relational database and 4GL app builder, sold continuously since the 1980s; now at R:BASE 11.

Hughes Technologies' lightweight 1994 SQL server that powered early dynamic websites before MySQL.

Embedded, transactional key-value and JSON document engine in a single C file, with Jx9 scripting.

Embedded in-memory and hybrid database for devices, real-time systems and time-series analytics.

Embeddable in-memory key/value store for Go with ACID transactions, custom and spatial indexes, and TTLs.

Fast Flutter/Dart object database with rich indexed queries, now stalled upstream.

Commercial embedded and client/server SQL database for Delphi and C++Builder, successor to FlashFiler.

Pure-Go embedded key-value store with Bitcask storage and Redis-like lists, sets and sorted sets.

D. J. Bernstein's constant database: immutable on-disk hash tables with two-read lookups and atomic swaps.

In-memory RDF store with incremental Datalog reasoning, now owned by Samsung.

Boiler Bay's all-Java embedded B-tree database with a ConcurrentNavigableMap API and a server edition.

Embedded BSON document database for Rust with a MongoDB-like API and optional wire-protocol server.

Enterprise object database formerly known as Versant, sold by Actian for complex object models.

Lightweight Go graph database with GraphQL, an SQL-like query language, full-text search and scripting.

ByteDance's RocksDB-compatible key-value engine built around Terark's searchable compression.

Compact in-memory and flash relational DBMS for embedded, telecom and SCADA systems, sold by Enea.

Veteran embedded SQL RDBMS for RTOS and Unix devices, still sold but with little visible development.

Chinese Java OLTP database derived from H2, now repositioned as an AI agent platform built on its SQL engine.

Embeddable C++ graph database library from Sparsity Technologies, refocused on embedded and mobile.

MIT-licensed RDF triple store for .NET with SPARQL and a LINQ-based entity framework; dormant since 2020.

Embedded NoSQL document store for Java and Android with pluggable MVStore or RocksDB storage.

Dependency-free PHP library that stores schemaless documents as plain JSON files on disk.

Couchbase's HB+-trie key-value storage library; no longer actively developed.

Simple Android key-value store that persists plain Java/Kotlin objects with Kryo; no SQL, no schemas.

Embedded Go key-value store tuned for read-heavy workloads, using linear hashing and an mmap'd index.

Compact German SQL RDBMS from Transaction Software, with a Z-curve multidimensional index (Hypercube).

Structured static database for game data: spreadsheet-style editor, typed sheets and diff-friendly JSON.

McObject's embedded object database for Java and .NET, dual-licensed GPL or commercial.

Yahoo's embedded Java key-value store: off-heap index of every key plus append-only data files.

Carlo Strozzi's 1998 shell-based relational database of plain-text tables and Unix pipe operators.

Embedded Java hypergraph database where edges can link any number of atoms, including other edges.

Yahoo's memory-mapped, zero-copy key-value library, a heavily tuned descendant of SGI's DBM.

Header-only C++11 append-only key-value store tuned for random reads on SSDs, built for the XRP Ledger.

Embeddable C datastore with 70+ Redis-like commands and a single-file ACID key-value store.

FAL Labs' C++ DBM library with hash and B+tree files; superseded by its author's Tkrzw.

Tiny embeddable C string key-value database from the radare2 project, built on djb's cdb format.

Embedded, single-file SQL database for .NET with a T-SQL dialect and ADO.NET provider.

Embeddable persistent and in-memory key-value engine for the JVM with typed Scala and Java APIs.

Paradigma Software's multi-engine server: ValentinaDB, DuckDB and SQLite plus report and form servers.

Small embeddable Java graph database for TinkerPop: in-memory, ACID, persisted to readable JSON text files.

JVM-embeddable distributed SQL database replicated with Apache BookKeeper and ZooKeeper.

PHP library that treats JSON files as database tables, with an ORM-style query builder and relations.

Objective-C object database with Git-like branching, tree-structured undo and semantic merging built in.

Ruby transactional document store that keeps every change as a commit in a Git repository.

Desktop 'true relational' DBMS implementing Date and Darwen's Tutorial D, for teaching and prototyping.

Tongue-in-cheek but working C/Go key-value store: mmap hash table, LZ4, splay-tree cursors and a REST API.

Memory-mapped constant database: a faster, thread-safe, >4 GB rewrite of D. J. Bernstein's cdb.

C# .NET object database with a graph layer (VelocityGraph); last release 11.1.1 in 2022.

Small Java key/value API for JSON objects over LevelDB, RocksDB, LMDB or MySQL; abandoned in 2014.

Lightweight Java document database usable embedded (including Android) or as a REST server.

Experimental lock-free in-memory MVCC key-value store for Go built on a Bw-tree; untouched since 2016.

Single-file PHP flat-file database that stores tables as TSV files and runs a tiny SQL-like dialect.

FairCom's embeddable ISAM, SQL and JSON database engine, now sold as FairCom DB; roots in 1984's c-tree.

Royalty-free embedded and client/server SQL engine for Delphi, C++Builder, Lazarus, .NET, ODBC and PHP apps.

Embedded transactional table-style document database for Java and .NET, including Android and Unity.

Embedded time-series and relational database for microcontrollers, RTOS and edge AI devices.

Apache ActiveMQ Classic's built-in journal-plus-B-tree message store; a persistence engine, not a general DB.

Russian certified relational DBMS from RELEX, used in secure government, defence and real-time systems.

Kellerman Software's commercial embedded object/relational database for .NET, Xamarin and Unity apps.

Ekky Software's embedded C++ object database with B+tree, spatial, full-text and pattern indexes.

Small-footprint embedded database with SQL and network-model APIs for RTOS, edge and safety-certified devices.

Pure-Java embedded SQL database with a JDBC 3.0 interface for desktop apps; last release in 2011.

Tiny main-memory SQL database for Windows and Linux built to make unit testing easy; last updated 2003.

Small Windows RDF store with SPARQL, SPARQL/Update and Datalog rule inference, embeddable via Lua or DLL.

Open-source retrieval database for AI apps, from embedded Python to serverless Chroma Cloud.

Open-source backend in one Go binary: SQLite database, auth, files, realtime and admin UI.

ACID document database for .NET and beyond, with auto-indexing, Corax search and multi-master replication.

Rust multi-model database (documents, graph, vectors, live queries) that runs embedded, in WASM or clustered.

Low-maintenance embeddable RDBMS with built-in TimeSeries, still quietly running retail and telco systems.

Tiny TypeScript full-text, vector and hybrid search engine for browsers, servers and the edge.

Lightweight, fast native XML database and XQuery 3.1/4.0 processor with a GUI.

Multi-model Java database speaking SQL, Cypher, Gremlin, MongoDB and Redis protocols.