SCIM (System for Cross- domain Identity Management) is a protocol that offers improved security and better user experience through automated user provisioning. However, implementing SCIM in-house can be challenging due to different providers' varying interpretations and implementations of the protocol. Key best practices include addressing data fragmentation, handling inactive users, ensuring scalability, and implementing robust error handling and testing procedures. Additionally, using TLS 1.2 for security, securing authentication and authorization, and outsourcing implementation to a provider that has already solved the problem can be beneficial.