Fig. 1. Diagram for optimization of the performance of the Neo4j graph database. Bottom layer: file open limit optimization; Neo4j often produces many small and random reads when querying data. Middle layer: page cache sizing; if all, or at least most, of the graph data files from a hard disk are cached into memory, it will reduce disk access and result in optimal performance. Top layer: heap sizing; it is beneficial to set a large heap space to support various query operations. OS, operating system; JVM, Java Virtual Machine.