db={menus:[{"_id":ObjectId("620323fe80ec16abea7a0205"),"name":"A new menu","description":"","menuData":[{"catName":"Cat 2","items":["61ded42461b1d8966c5efc45","61ded55001e3cafb8db19198","61df9adf2441b6113033f341","61dfa8c82441b6113033f738"]},{"catName":"Cat 1","items":["62020691adda4aab89f1742d","61dfa8c82441b6113033f738"]}],"status":"active",}],menuitems:[{"_id":ObjectId("61ded55001e3cafb8db19198"),"name":"Coca-Cola 600ml","description":"Refreshing taste...ahhh","price":3.95,"tags":["drinks"],"options":[],"status":"active",}]}

db.menus.aggregate([{"$match":{"_id":ObjectId("620323fe80ec16abea7a0205")}},{"$addFields":{"newField":"$menuData.items"}},{"$unwind":{"path":"$newField"}},{"$lookup":{"from":"menuitems",let:{newField:"$newField"},pipeline:[{$match:{$expr:{$in:[{$toString:"$_id"},"$$newField"]}}}],"as":"items"}}])