neo4j

Neo4j

Neo4j is a native graph database. It stores data as nodes and relationships, not tables or documents. It is essential for "connected data" problems where relationships are as important as the data itself.

When to Use

• Complex Interconnected Relationships: Social networks, recommendation engines, identity and access management (IAM), and supply chains.
• Fraud Detection & Graph Analytics: Detecting ring fraud, circular payment transfers, and money laundering paths in milliseconds.
• Knowledge Graphs & Graph RAG: Connecting enterprise knowledge bases to LLMs using Graph Retrieval-Augmented Generation.
• Real-Time Pathfinding & Network Routing: Calculating shortest paths, dependency trees, and network topology bottlenecks.

Quick Start

-- Create nodes and relationships
CREATE (alice:Person {name: 'Alice'})
CREATE (bob:Person {name: 'Bob'})
CREATE (alice)-[:KNOWS {since: 2024}]->(bob);

-- Query friends of friends
MATCH (p:Person {name: 'Alice'})-[:KNOWS]->(friend)-[:KNOWS]->(fof)
RETURN fof.name;

Core Concepts

Labeled Property Graph (LPG) Model

Vertices are Nodes with Labels; connections are directed Relationships with Types; both store arbitrary key-value Properties:

(:Person {name: "Alice"}) ──[:MANAGES {since: 2023}]──→ (:Person {name: "Bob"})

Cypher Query Language Graph Matching

Declarative pattern matching queries relationships visually:

// Discover friends of friends who like Graph Databases but Alice does not know yet
MATCH (alice:Person {name: 'Alice'})-[:FRIEND]->(f:Person)-[:FRIEND]->(fof:Person)
WHERE NOT (alice)-[:FRIEND]->(fof) AND alice <> fof
MATCH (fof)-[:INTERESTED_IN]->(:Topic {name: 'Neo4j'})
RETURN fof.name AS recommendation, count(f) AS mutualFriends
ORDER BY mutualFriends DESC
LIMIT 10;

Graph Data Science (GDS) Algorithms

Executes graph algorithms (PageRank, Community Detection, Shortest Path) natively in memory:

// Run PageRank on projected graph projection
CALL gds.pageRank.stream('fraudNetwork')
YIELD nodeId, score
RETURN gds.util.asNode(nodeId).accountNumber AS account, score
ORDER BY score DESC
LIMIT 20;