Neo4j is being used by NTT Data Services to implement deep access control, a critical area that handles complex security and access management. The company has partnered with Neo4j to analyze and manage access controls for various clients, including those with 5,000 to 10,000 users. By moving raw data into Neo4j, they can easily identify loop points and determine if a person should have access to certain areas. This approach also helps when a new employee joins or leaves the company, ensuring that their access is properly managed. Manish Jain, from NTT Data Services, finds Neo4j's graph technology particularly useful for this analysis, as it allows for easy comparison between old and new solutions, and can convert large databases into Neo4j, saving storage and improving performance.