Minor - P4 https://docs.mongodb.com/manual/tutorial/project-fields-from-query-results/
db.inventory.find({"item":"postcard"}, {_id:0, instock:{$slice:1}})
returned
{ "item" : "postcard", "status" : "A", "size" : { "h" : 10, "w" : 15.25, "uom" : "cm" }, "instock" : [ { "warehouse" : "B", "qty" : 15 } ] }
it was expected to return
{"instock" : [ { "warehouse" : "B", "qty" : 15 } ] }