Databases for Transactional apps (OLTP)

The extensible, standards-first open-source relational database.

The web's default open-source SQL database, now on calendar versioning with 9.7 as the LTS line.

The default document database: flexible BSON documents, rich queries and built-in sharding.

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

Microsoft's flagship RDBMS: T-SQL, columnstore, Always On, and now native vectors and JSON.

Google's app platform: Firestore, Realtime Database and Data Connect, plus auth, functions and hosting.

The enterprise heavyweight: RAC, Data Guard and a converged engine for SQL, JSON, graph and vectors.

Community-led MySQL fork with extra storage engines, built-in Galera and a faster feature cadence.

Open-source Postgres backend platform: database, auth, storage, realtime and edge functions in one project.

Serverless document database with realtime listeners, offline SDKs and a new Enterprise edition.

Postgres-wire distributed SQL built to survive node, zone and region failures with serializable transactions.

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

IBM's enterprise RDBMS for Linux, UNIX, Windows and z/OS, with BLU columnar and pureScale clustering.

Microsoft's globally distributed, multi-API NoSQL and vector database with SLA-backed latency.

HTTP/JSON document database built around multi-master replication and offline-first sync.

SAP's in-memory columnar HTAP database, the mandatory engine under S/4HANA.

MySQL-compatible distributed SQL with a row store for OLTP and a columnar replica for real-time analytics.

Google's globally consistent, horizontally scaling SQL service with graph, vector and full-text built in.

Microsoft's always-current managed SQL Server engine, from free serverless databases to 128 TB Hyperscale.

Open-source JSON database that pushes live query results to apps through changefeeds.

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

Apache-licensed distributed SQL that reuses the PostgreSQL query layer on a Raft-replicated storage engine.

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

IBM's managed, CouchDB-compatible JSON database with built-in search and geospatial queries.

Low-code database app builder for Mac, Windows, iPad and web, owned by Apple's Claris.

The original microcomputer database and xBase language, still sold as a Windows IDE built on DBF tables.

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

Serverless Postgres with copy-on-write branching and scale-to-zero, now part of Databricks.

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

Distributed SQL mixing in-memory rowstore and columnstore for real-time analytics, search and vectors.

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

The original Sybase T-SQL engine, still running trading and SAP systems but firmly in SAP's sunset lane.

Memory-first distributed JSON database with SQL++, search, vector indexes and mobile sync.

Open-source distributed SQL from Yandex combining row and column tables, topics and vector search.

In-memory relational database that runs your server logic as WASM modules and streams changes to clients.

Open-source backend platform with databases, auth, storage, functions and realtime, self-hosted or cloud.

AWS's managed service for six relational engines: PostgreSQL, MySQL, MariaDB, Oracle, SQL Server and Db2.

Firebase's original JSON-tree database that syncs every change to connected clients in milliseconds.

Reactive TypeScript backend with a transactional document database, server functions and live queries.

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

Apple's iCloud record store for apps: private per-user data, a public database and built-in sync.

Performance-focused managed MySQL (Vitess) and Postgres, with NVMe-backed Metal clusters and branching.

AWS's MySQL- and PostgreSQL-compatible engine on a shared, six-way replicated storage layer.

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.

A drop-in MySQL build that ships enterprise features (thread pool, audit, encryption) as free GPL code.

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

Enterprise multi-model database for XML, JSON and RDF with built-in search and semantic RAG.

CNCF-graduated sharding and clustering layer that makes a fleet of MySQL servers look like one database.

Postgres extension that shards tables across nodes for multi-tenant SaaS and real-time analytics.

Query-driven sync engine: clients run ZQL locally against a Postgres-backed cache for instant UIs.

In-memory, partitioned SQL engine running Java stored procedures serially for millisecond decisioning.

Integrated RDBMS plus ABL 4GL application platform behind thousands of ERP and vertical business apps.

Alipay-proven distributed SQL with MySQL (and Oracle, in Enterprise) compatibility, HTAP and vector search.

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

MySQL-compatible SQL database you can branch, diff, merge and clone like a Git repository.

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

One of the original relational databases, still sold by Actian for long-lived enterprise systems.

AWS's managed MongoDB-API database on a proprietary, Aurora-style storage layer.

MongoDB's own multi-cloud DBaaS, bundling search, vector search and stream processing.

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

Oracle's engineered system for Oracle Database, with smart storage offload for OLTP and analytics.

Immutable Datalog database from Nubank where every fact is timestamped and queries run in the app process.

Serverless, active-active distributed SQL on AWS with PostgreSQL compatibility and no instances to size.

Serverless Postgres from the Prisma ORM team, on unikernels, billed per operation with no cold starts.

Lightweight distributed database that replicates SQLite over Raft behind a simple HTTP API.

Open-source backend platform on Postgres with Hasura GraphQL, auth, storage and functions.

Managed, distributed SQLite with pub/sub, edge functions and CRDT sync to on-device databases.

Multi-model data platform (SQL, objects, globals, vectors) with built-in interoperability, big in healthcare.

EnterpriseDB's PostgreSQL with deep Oracle compatibility: PL/SQL packages, DBMS_* and TDE.

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

A wire-compatible SQL cache for Postgres and MySQL that keeps cached queries fresh from replication.

Alpha-stage, Vitess-inspired sharding, pooling and HA layer for unmodified PostgreSQL, led by Supabase.

Version-controlled SQL database with PostgreSQL compatibility: branch, diff and merge your tables.

Elastic distributed SQL with in-memory transaction engines and separate storage managers, owned by Dassault.

Korean open-source RDBMS with built-in HA and Oracle-like SQL, common in Korean public sector.

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

Shared-nothing, auto-sharded in-memory MySQL engine built for telecom-grade availability.

Cloud-native storage engine for PostgreSQL with undo logs, no VACUUM bloat and row-level WAL.

Bloomberg's clustered relational database with optimistic concurrency and synchronous replication.

Google Cloud's managed MySQL, PostgreSQL and SQL Server, with an Enterprise Plus tier for fast failover.

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

Percona Server plus Galera synchronous replication, packaged as an open-source HA MySQL cluster.

Fully open-source multi-master distributed PostgreSQL built on the Spock logical replication extension.

SAP's older relational database (ex-Adabas D/SAP DB), still under content servers and liveCache.

Synchronous multi-primary replication for MySQL and MariaDB, now owned by MariaDB plc.

Apache sharding middleware that adds sharding, read/write splitting and encryption over MySQL or Postgres.

Apache-licensed MongoDB-protocol proxy that stores data in PostgreSQL with the DocumentDB extension.

Oracle's in-memory relational database: microsecond SQL, PL/SQL, and a cache tier for Oracle Database.

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

Serverless Postgres that makes tenants a first-class primitive, with per-tenant isolation and placement.

Node.js runtime that fuses database, cache, app logic and MQTT/WebSocket messaging in one process.

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

Bitemporal SQL database on object storage that keeps every version of every row.

The commercial, enterprise-hardened distribution of Apache Ignite for low-latency SQL and compute.

Open-source Postgres platform with storage-level copy-on-write branching, scale-to-zero and anonymized clones.

Huawei's distributed enterprise RDBMS built on openGauss, aimed at replacing Oracle in Chinese finance.

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

China's leading home-grown RDBMS; DM9 (2026) adds distributed, HTAP and AI features.

Huawei-originated open-source RDBMS forked from PostgreSQL, with in-memory and column engines.

1980s PC relational database and RAD tool, still sold today with builds for legacy DOS and Windows apps.

A Postgres extension that keeps materialized views updated incrementally inside the same transaction.

MySQL-compatible cloud-native HTAP database on object storage, with vector search and snapshots.

Drop-in MongoDB Community build with enterprise features like encryption, LDAP and hot backup.

Serverless SQLite for Cloudflare Workers, priced per row read and written, with read replicas and time travel.

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

Korean hybrid in-memory/on-disk RDBMS for telecom and finance, closed-source again since 2023.

Apache-licensed PostgreSQL distribution with an Oracle-compatible mode, PL/iSQL and Oracle packages.

MIT-licensed, MongoDB-compatible document engine built as PostgreSQL extensions, run by the Linux Foundation.

Alibaba's open-source, MySQL-compatible shared-nothing distributed SQL with Paxos and columnar indexes.

Microsoft's managed community PostgreSQL, with zone-redundant HA, DiskANN vectors and Citus elastic clusters.

DEC's relational database for OpenVMS, owned by Oracle since 1994 and still updated on Alpha and Itanium.

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

Lets PostgreSQL understand SQL Server's T-SQL and TDS protocol, so SQL Server apps can migrate.

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

The relational database built into IBM i (AS/400), integrated with the OS and object security.

Fault-tolerant, shared-nothing SQL on HPE NonStop, built for payment switches that can never go down.

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

Byzantine-fault-tolerant, blockchain-backed SQL database built on SQLite; dormant since 2021.

Google's Postgres-compatible service with disaggregated storage, a columnar engine and ScaNN vectors.

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

SQL Server's built-in lock-free, memory-optimized OLTP engine with natively compiled T-SQL.

Chinese distributed document database with native ACID storage, SQL instances and S3 API, used in many banks.

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

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

Alibaba Cloud's shared-storage relational service in MySQL-, PostgreSQL- and Oracle-compatible editions.

Expensify's WAN-replicated SQLite server with Paxos leader election, MySQL protocol and job/cache plugins.

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

Baidu's MySQL-compatible distributed HTAP database on RocksDB and Raft, with full-text and vector indexes.

1988 DOS-era SQL server built for IBM DB2 compatibility; lives on inside Micro Focus mainframe tools.

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

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

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

Downloadable Spanner that runs on your own servers, other clouds or a laptop, with Paxos and auto-sharding.

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

Self-tuning document-graph database with automatic indexing, full version history and time-travel reads.

Managed horizontal sharding for Aurora PostgreSQL: one endpoint over a serverless group of shards.

Databricks' serverless Postgres built on Neon tech, with branching and sync to Delta tables in Unity Catalog.

Korean Oracle-compatible RDBMS with RAC-style Active Cluster, popular for Oracle exits in Asia.

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

Oracle's managed MySQL with an in-memory columnar engine for analytics, lakehouse, ML and vector search.

One developer's ISO-SQL relational server written in Delphi, with MVCC; open-sourced under GPL in 2012.

Crunchy Data's developer-friendly managed Postgres across AWS, GCP and Azure, now owned by Snowflake.

Proprietary ACID 'algorithmic' database from Indianapolis claiming extreme speed without conventional indexes.

Microsoft's managed MongoDB-compatible service, built on the open-source DocumentDB engine.

Keyed-file ISAM database plus SQL engine bundled with BASIS International's BBj Business BASIC platform.

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

Couchbase's managed DBaaS: Couchbase Server clusters plus App Services sync and AI tooling.

SYSCOM's ODBC-native SQL database from Taiwan, known for letting COBOL programs use SQL tables.

Low-cost Windows desktop database in the Access mould: tables, forms, reports and LAN multi-user access.

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

Chinese commercial database family: GBase 8a analytics, 8s transactional cluster, 8c distributed.

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

Chinese PostgreSQL-derived RDBMS with Oracle, MySQL and SQL Server compatibility modes.

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

Self-driving Oracle Database on Exadata: auto-patching, auto-scaling, and Select AI, on OCI and other clouds.

Russian commercial PostgreSQL distribution with multimaster, 64-bit XIDs and compressed storage.

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.

Low-cost Informix-SE and ESQL/C compatible SQL engine for Linux, UNIX, Windows and VMS from Infoflex.

Cincom's mainframe relational DBMS for high-volume OLTP, the SQL half of the SUPRA family.

Tencent's financial-grade MySQL-compatible database family: distributed TDSQL and cloud-native TDSQL-C.

AWS's serverless key-value and document store with single-digit-millisecond reads at any scale.

Masterless wide-column database built for always-on writes across data centers.

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

The standard spatial extension for PostgreSQL: geometry, geography, rasters and topology in SQL.

C++ rewrite of Cassandra with shard-per-core design; also speaks the DynamoDB API.

Flash-optimized distributed key-value and document database for predictable sub-millisecond latency at scale.

Native multi-model database: documents, graphs, search and vectors behind one query language.

The standard Postgres extension for vector similarity search with HNSW and IVFFlat indexes.

Apple's ordered, strictly serializable distributed key-value store, built to have layers on top.

Google's managed wide-column store, the original Bigtable, with HBase API and SQL access.

A distributed, memory-first SQL database and compute grid; Ignite 3 rebuilt it around Raft and Calcite.

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

Strongly typed entity-relation database with TypeQL, polymorphic queries and a Rust core.

Hadoop's Bigtable clone: strongly consistent wide-column tables on top of HDFS.

Distributed, horizontally scalable graph database in Go with native GraphQL and DQL.

In-memory database and Lua application server in one process, with an optional disk engine.

CNCF-graduated, Raft-replicated transactional key-value store in Rust; the storage layer of TiDB.

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

PostgreSQL extension that adds openCypher graph queries alongside SQL.

Purpose-built financial transactions database: double-entry accounts and transfers at very high throughput.

A purpose-built event store for event sourcing, with streams, subscriptions and projections.

Erlang-based, Dynamo-style key-value store built to stay up through ugly failures.

Immutable, tamper-evident database with cryptographic proofs, offering key-value, SQL and document APIs.

Sorted, distributed key-value store on HDFS with cell-level security labels.

AWS's managed graph database speaking Gremlin, openCypher and SPARQL on shared storage.

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

TigerData's Postgres extension adding StreamingDiskANN indexes on top of pgvector.

Oracle's sharded key-value and JSON store, available as Apache-licensed software or an OCI service.

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

Disk-friendly Postgres vector extension using IVF + RaBitQ, the successor to pgvecto.rs.

The open-source core of GemFire: a consistent, partitioned in-memory data grid for Java.

Serverless Cassandra-as-a-service with vector search and a JSON Data API, now owned by IBM.

Rocket's Pick-style MultiValue databases, powering thousands of vertical business applications.

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

Toshiba's memory-first container database for IoT time series, with per-container ACID and SQL.

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

Inverted-list, multi-value mainframe database paired with Natural, run as a standalone Software AG business.

PostgreSQL fork with a built-in property graph model, mixing SQL, openCypher and ISO GQL.

FIS's high-throughput M (MUMPS) database and compiler, behind major core-banking systems.

Open-source MUMPS/M hierarchical key-value database forked from GT.M, with SQL via Octo.

IBM's 1960s hierarchical database and transaction manager, still running bank and airline cores on z/OS.

Ant Group's open-source C++ graph database with ACID transactions, Cypher and LDBC-record performance.

Single-threaded stateful actors at the edge, each with its own strongly consistent SQLite store.

CODASYL network-model mainframe database, now Broadcom's, still running decades-old COBOL systems.

Smalltalk object database where application code runs inside the transactional object repository.

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

New Zealand's integrated object database, language and app server for building line-of-business systems.

Broadcom's commercial in-memory data grid, the enterprise build of Apache Geode.

GigaSpaces' Java in-memory data grid with space-based processing, SQL queries and tiered storage.

Rocket Software's mainframe inverted-list DBMS, in production since 1972 and still getting releases.

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

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

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

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

Netflix's Dynamo-style proxy layer that adds sharding and multi-datacenter replication to Redis and Memcached.

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

In-memory .NET application platform where C# classes are database tables, with no ORM in between.

A durable, Valkey/Redis-compatible in-memory database on AWS backed by a multi-AZ transaction log.

Serverless, CQL-compatible Cassandra service on AWS with no clusters to manage.

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

Gremlin graph layer on the Aerospike database for billion-edge graphs with predictable latency.

Schema-less multi-model engine from Germany's Cortex AG, now sold as CortexEngine within Cortex-IP.

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

MultiValue database that compiles Pick BASIC to native code, now part of Rocket's MV portfolio.

RUN Software's terminology-oriented object database for C++ and .NET, still released on SourceForge.

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

Compact MultiValue (Pick) database from Ladybridge, once GPL-licensed, now Rocket's entry-level MV product.

Managed hosting for Neo4j Community Edition on dedicated cloud instances, with backups and replicas.

Multi-user object database for Squeak and Pharo Smalltalk, written entirely in Smalltalk.

Twitter's in-house, multi-tenant, eventually consistent key-value store with pluggable storage engines.

The original commercial Pick MultiValue database (1973), still sold and updated by NEC Software Solutions.

The direct descendant of the original Pick system: a MultiValue database and environment on Linux and Windows.

Fujitsu BS2000 mainframe DBMS combining a CODASYL network model with SQL on the same data.

IBM's Java in-memory data grid for caching, HTTP sessions and partitioned object storage; still patched.

The default property-graph database, with Cypher, a big ecosystem and a managed cloud.

Elasticsearch-quality BM25 search and fast aggregations inside Postgres via the pg_search extension.

Shared-nothing distributed graph database for trillion-edge graphs, with GQL in Enterprise v5.

Rust graph-vector database on object storage, queried through typed SDKs for AI apps.

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