db={"prefix":[{"_id":"648c39f13af539b8dfebdf9d","categoryId":["648468306806396cd3ab9710","648850199e779dfd371a2766"],"name":"Test Name",}],"categories":[{"_id":"648468306806396cd3ab9710","name":"Cat A",},{"_id":"648850199e779dfd371a2766","name":"Cat B",},]}

db.prefix.aggregate([{"$set":{"cat_ids":{"$map":{"input":"$categoryId","as":"item","in":{"$toObjectId":"$$item"}}}}},{"$lookup":{"from":"categories","localField":"categoryId","foreignField":"_id","pipeline":[{$project:{_id:1,name:1}}],"as":"categoryDetail"}}])