Which is better for Mongo: empty field or no field at all?

Question

In MongoDb - in case i have fields that are not always contain values - which is better practice: keep same fields in all records even if sometimes those fields are empty or not create those field at all?

10x!

Answer 1

The fields will occupy disk space for the key, even if there is no value, so better do not include them; unless you need to find what documents does not contain such field / contain empty field

MongoDB is schemaless and each document in the collection can have different fields, as long as that makes sense for your application.