MongoDB 'masters' cross joins by embedding sizes into every fit: because duplicating tiny clothing data screams scalable genius

In the realm of NoSQL databases, MongoDB offers a flexible approach to performing cross joins, a concept traditionally associated with relational databases. By utilizing the `$lookup` aggregation operator without a filter condition, developers can generate all possible combinations of data from two collections. For instance, combining clothing sizes and gender-specific fits can produce a comprehensive list of product variants. MongoDB's approach allows for modeling choices at read time, write time, or in the application itself, differing from the rigid normalization of relational databases. This flexibility enables developers to adapt to evolving business rules and access patterns, such as defining distinct sizes for men and women without altering the data model. With MongoDB, consistency is maintained by the application's service rather than through cross-table constraints, making it an attractive option for domain-driven applications with clear ownership of data. This approach streamlines data retrieval and updates, eliminating the need for joins or multiple queries.