MongoDB's flexible document structure is beneficial for custom e-commerce feature development, allowing developers to easily add fields without database migrations. The platform's schema-less design enables faster prototyping and query on any document field, even embedded documents. MongoDB also offers a way to create data relationships without joins, using callback methods or simple/complex queries. While it lacks atomic transactions across collections, optimistic locking is sufficient for low-moderate data contention. This approach can reinvent open source e-commerce with reduced complexity and improved performance.