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Cayley

Cayley is an open-source graph database for storing and querying connected data.

Place
#18 of 39
Score
6.2
Cayley's website

What Cayley is

Cayley is an open-source graph database for storing and querying connected data. It supports RDF and linked-data formats such as NQuads and JSON-LD, with Gizmo, MQL, and a GraphQL dialect available for queries. Cayley can use SQL, NoSQL, or key-value storage, and its listed database backends include PostgreSQL, MySQL, SQLite, MongoDB, LevelDB, Bolt, and others. The project can be extended with additional formats, backends, query languages, or custom logic. Its tools include a query editor, a REPL, and a visualizer that can display graph results when they are tagged with source and target. Documentation also describes HTTP query endpoints for Gizmo, GraphQL, and MQL. Cayley is available for web, API, Linux, macOS, and self-hosted use. It is free to use in any project under the Apache 2.0 license. The default in-memory store is suited to data that fits in machine memory and does not need persistence; Bolt is recommended for larger datasets or persistent workloads. Installation guidance covers Ubuntu via Snap, macOS via Homebrew, Docker, and source builds.

Good

  • Supports RDF, NQuads, and JSON-LD.
  • Offers Gizmo, MQL, and GraphQL-dialect queries.
  • Works with SQL, NoSQL, and key-value storage.
  • Includes a query editor, REPL, and visualizer.
  • Free to use under Apache 2.0.

Watch out

  • The default in-memory store is not persistent.
  • Large or persistent workloads are directed to Bolt.
  • Graph visualization requires source and target tags.

Who it suits

Cayley suits developers who need an extensible graph database and want a choice of query languages and storage backends. It may also appeal to teams working with RDF or linked data who can choose a storage setup appropriate to their persistence needs.

Verdict

Cayley offers several ways to query and store graph data, along with tools for inspecting results. Choose storage with care: its default in-memory option is intended for data that needs no persistence.

Plans and prices

From Cayley's own pricing page, checked 4 Oct 2026.

All about pricing
PlanPriceWhat it gives you
Open-source CayleyGraphFreeFree to use in any project · Apache 2.0 license

The facts

Each one read from Cayley's own pages, with the date it was checked.

What it does

API
Cayley's documentation describes HTTP query endpoints for Gizmo, GraphQL, and MQL.checked 4 Oct 2026
Database integrations
The configuration guide lists LevelDB, Bolt, MongoDB, Elasticsearch, CouchDB, PouchDB, PostgreSQL, CockroachDB, MySQL, MariaDB, and SQLite backends.checked 4 Oct 2026
Data size guidance
The guide says the default in-memory store is best for datasets that fit in machine memory and workloads that do not require persistence; it recommends Bolt for large datasets or persistent workloads.checked 4 Oct 2026
Extensibility
Cayley can be extended with new formats, backends, query languages, or custom logic.checked 4 Oct 2026
Installation
The installation guide gives instructions for Ubuntu via Snap, macOS via Homebrew, Docker, and building from source.checked 4 Oct 2026
License
Cayley is developed under the Apache 2.0 license and is free to use in any project.checked 4 Oct 2026
Linked data
Cayley supports RDF and linked data formats including NQuads and JSON-LD.checked 4 Oct 2026
Query languages
Cayley supports Gizmo, described as a Gremlin dialect, MQL, and a GraphQL dialect.checked 4 Oct 2026
Query tools
Cayley includes a query editor, visualizer, and REPL.checked 4 Oct 2026
Storage
Cayley works on top of SQL, NoSQL, or key-value databases.checked 4 Oct 2026
Support and community
The project invites users to join its community on Slack or Discourse.checked 4 Oct 2026
Visualization
The UI overview says the visualizer can display query results as a graph when results are tagged with source and target.checked 4 Oct 2026
What it does
Cayley is an open-source graph database inspired by the graph database behind Freebase and Google's Knowledge Graph.checked 4 Oct 2026

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