Neo4j 4.0 is a major release that has taken over a year of work and has significantly improved the database's performance, scalability, and security. The new reactive data architecture allows for faster development, while the multi-database feature enables running multiple databases concurrently in a cluster or server, providing better isolation and flexibility. Additionally, Neo4j Fabric provides distributed queries across multiple databases, making it easier to process large datasets. The schema-based security model is also noteworthy, offering granular access control and preserving data integrity by considering the structure of the graph. This release is expected to make Neo4j more attractive to developers and users, providing a better experience for building fast, scalable, and secure applications.