Databases for Metadata & config

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.

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

The original coordination service: hierarchical znodes, watches and ephemeral nodes for clusters.

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

The key-value store built into HashiCorp Consul for service config, locks and discovery.

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

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

Raft-based, strongly consistent key-value store that holds Kubernetes' cluster state.

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

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

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.

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

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

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

Git-for-data document and knowledge-graph database with branches, diffs and time travel.

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

Cheap, schemaless key-attribute store inside an Azure Storage account.

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

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

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

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

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

AWS's original 2007 schemaless attribute store; still running but frozen in time.

Standards-compliant RDF triplestore with reasoning, connectors and MCP support for GraphRAG.

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

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

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

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

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

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

Apache's Java Content Repository: a hierarchical, versioned node store with search, behind many Java CMSs.

Enterprise knowledge-graph platform: RDF store, reasoning and virtual graphs over your sources.

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

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

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

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.

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

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

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

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.

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

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

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

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

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

Deductive object base for metamodeling, built on O-Telos with Datalog rules and unlimited meta-levels.

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

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

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

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

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

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

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

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.

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

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.

The original SQL-on-Hadoop warehouse, now mostly valued for its Metastore and Iceberg support.

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

Hybrid SQL/RDF engine that runs many of the largest public SPARQL endpoints.

Open-source native XML database and XQuery application platform for documents and digital editions.

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

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

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

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

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

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