PROD_updateNamesToUpperCase

var bulk = db.users.initializeOrderedBulkOp();
var count = 0;

db.users.find({}).forEach(function(doc) {
    bulk.find({ "_id": doc._id }).updateOne({
        "$set": {
            "last_name": doc.last_name.toUpperCase(),
            "first_name": doc.first_name.toUpperCase()
        }}
    );

    count++;

    if ( count % 500 == 0 ) {
        bulk.execute();
        bulk = db.users.initializeOrderedBulkOp();
        count = 0;
    }

});

if ( count > 0 )
    bulk.execute();