Cayley is an open-source graph database designed for Linked Data that draws inspiration from the graph database architecture behind Google's Knowledge Graph.
The tool addresses the need to store and query highly connected data in the form of triples or quads. Cayley models data as a graph where relationships between entities can be traversed efficiently. It provides multiple query languages to suit different preferences and use cases: Gizmo, which is inspired by Gremlin; a GraphQL-inspired query language; and MQL, a simplified option for those familiar with Freebase. The database includes a built-in query editor, visualizer, and REPL for interactive exploration.
Cayley suits projects that work with semantic web data, knowledge graphs, or any application requiring efficient traversal of interconnected information. The tool is modular, allowing integration with various programming languages and backend storage systems. It has been deployed in production environments by multiple companies. Developers should note that the tool is optimized for application-level performance rather than extreme scale; performance testing indicates it handles hundreds of millions of quads effectively, with multi-hop intersection queries completing in the range of 150 milliseconds on consumer-grade hardware.
The project maintains active community channels including a Slack workspace, Discourse forum, and Twitter presence. Development activity shows consistent testing infrastructure with automated build and release workflows. The codebase is written in Go, which contributes to its deployment simplicity and performance characteristics. The project accepts community contributions through a documented contribution process.
