# Cayley — Open-Source Graph Database Inspired by Google's Knowledge Graph

> Cayley is an open-source graph database written in Go, inspired by the graph infrastructure behind Google's Knowledge Graph. It supports multiple storage backends and query languages for flexible graph traversal.

## Install

Save as a script file and run:

# Cayley — Open-Source Graph Database Inspired by Google's Knowledge Graph

## Quick Use
```bash
go install github.com/cayleygraph/cayley/cmd/cayley@latest
cayley http --dbpath=./data
# Open http://localhost:64210 for the web UI
```

## Introduction
Cayley is a graph database written in Go, originally created at Google and open-sourced for community use. It provides a flexible query layer supporting Gizmo (JavaScript-based) and GraphQL, backed by pluggable storage engines ranging from in-memory to PostgreSQL and MongoDB.

## What Cayley Does
- Stores and queries graph-structured data using subject-predicate-object triples (quads)
- Supports multiple query languages: Gizmo (JS), GraphQL, and MQL
- Pluggable backend storage: BoltDB, PostgreSQL, MongoDB, in-memory, and more
- Provides a built-in web UI for visual graph exploration and query execution
- Imports and exports standard RDF formats (N-Quads, JSON-LD, Turtle)

## Architecture Overview
Cayley uses a quad store model where each fact is stored as a quad (subject, predicate, object, label). The query layer compiles traversal expressions into an iterator-based execution plan that operates against a pluggable backend. Storage engines implement a common interface, allowing swaps between BoltDB for embedded use, PostgreSQL for durability, or in-memory stores for testing.

## Self-Hosting & Configuration
- Install via Go toolchain or download prebuilt binaries from GitHub releases
- Configure storage backend with `--dbpath` flag or YAML config file
- Default HTTP port is 64210; override with `--host` and `--port` flags
- Load initial data with `cayley load --quads=<file>` supporting N-Quads and JSON-LD
- Deploy with Docker using the official `cayleygraph/cayley` image

## Key Features
- Multiple query languages let teams pick what fits their mental model
- Pluggable backends mean you can start embedded and scale to PostgreSQL later
- Built-in web visualizer for interactive graph exploration
- Native Go library for embedding directly into Go applications
- RDF-compatible data model aligns with linked data standards

## Comparison with Similar Tools
- **Neo4j** — More mature with Cypher, but requires JVM and commercial license for clustering
- **Dgraph** — Distributed GraphQL-native DB with higher operational complexity
- **ArangoDB** — Multi-model but heavier; Cayley is lighter for pure graph workloads
- **Apache Jena** — Full semantic web stack in Java; Cayley is simpler and Go-native

## FAQ
**Q: What query language should I start with?**
A: Gizmo (JavaScript-based) is the most documented and flexible for traversals. GraphQL works well if you already know your schema.

**Q: Can Cayley handle large datasets?**
A: Yes, with PostgreSQL or MongoDB backends it handles millions of quads. For billions, consider a distributed graph DB instead.

**Q: Is Cayley still maintained?**
A: The project has slower release cadence but remains functional and accepts contributions.

**Q: Can I use Cayley as an embedded library?**
A: Yes, import the Go packages directly and use the graph API without running a server.

## Sources
- https://github.com/cayleygraph/cayley
- https://cayley.gitbook.io/cayley

---
Source: https://tokrepo.com/en/workflows/cayley-open-source-graph-database-inspired-google-s-4c55125e
Author: Script Depot