[{product:"Mobile Phone",store:"Electronics Store",total_quantity:5,locations:[{id:"loc1",quantity:3},{id:"loc2",quantity:2}]}]

db.collection.aggregate([{$addFields:{locations:{$filter:{input:"$locations",cond:{$ne:["$$this.id","loc1"]}}}}},{$addFields:{total_quantity:{$reduce:{input:"$locations.quantity",initialValue:0,in:{$add:["$$value","$$this"]}}}}}])