When using mongoimport, creating a document which contains dots in a key is possible. however, this should not be allowed, since it would never be queryable.

example
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mongoimport -d test -c invalidjson --file ivalid.json (use attached file)

This is allowed using mongoimport, but actually the document is invalid. Can you add a check on this when importing data? mongoshell is ok. that returns a correct error.