Nexus Knowledge Graph: A Dual-Backend Service with Runtime Repository Protocol
Nexus Knowledge Graph by Manazir Ali. A research-grade case study on the design and implementation of a typed personal knowledge graph exposed as a FastAPI service with a Typer CLI client. Reports a runtime-checkable Repository Protocol that admits two interchangeable backends (Neo4j 5 as the primary graph-native store and SQLite 3 as a zero-dependency fallback) without application-code awareness, a uniform breadth-first traversal endpoint that resolves to native Cypher variable-length paths on Neo4j and to an iterative Python simulation on SQLite, and a pre-seeded reference instance of 752 nodes and 1,122 typed relationships across 10 node types and 13 relationship types. 
