Create unique field
I need to guarantee that a field of a CustomObject is unique. In a workspace I can use a JS extension, which will tell the user right away that he must choose another value if it's duplicated.
This object can also be created through import. I can use a CPM associated to the object to validade if it is duplicated and change the value or delete the register if it is.
1) Using a CPM will not stop the creation of the record nor let the user know that he created an object with a duplicated value and that this record was changed or deleted. One possibility is using a custom script for the import, which would validate the values before creation. But I would rather not using this level of customization (users are used to the standart import tool and changes can always be a problem).