Mongoose _id exclusion from JSON serialization without removing document identity

Mongoose includes the _id field in query results and in output from toObject() and toJSON() by default. The goal is to keep _id available for internal document tracking and middleware while preventing it from being serialized into public API responses.

Other fields support select: false, but that option does not apply to _id. Setting { _id: false } at the schema level removes the identifier from the document entirely, which may break plugins or middleware that depend on document identity. No schema-level option appears to exclude _id only from JSON serialization while preserving it in memory.

Is there a supported global transformation or schema option that hides _id from toJSON() output without removing it from the document? Does defining a custom toJSON transform at the schema level affect middleware that reads _id before serialization? Are there behavior differences between Mongoose 6.x and 7.x regarding this serialization boundary?