MongoDB Realm's Flexible Sync is now available in preview, offering a more flexible sync experience that enables complex use cases without requiring custom code. This new iteration allows users to define data synced to user applications using language-native queries, supporting dynamic and overlapping queries based on user inputs. It also introduces document-level permissions, making it easier to limit access to specific documents based on a user's role. Additionally, Flexible Sync optimizes for real-time collaboration by treating single objects or documents as the smallest entity for synchronization, enhancing query performance and conflict resolution. The service is compatible with MongoDB 5.0 and is available now, with plans for future enhancements and integrations.