MongoDB actually has built-in schema validation which can be enabled, we're just not using it at the moment because we haven't yet found a good use case where the TypeScript schema itself is not enough.

The schema in Modelence is defined in your code, and at the moment the only use case where it's not enough is if someone directly modifies the database data externally. We're not against having the native MongoDB schema as an extra enforcement, the only reason we haven't added it yet is because it requires extra work to carefully sync both. I believe at some point we'll add it as an extra layer to prevent corrupting the data by direct modifications.