db={"inventory":[{item:"journal",qty:25,tags:["blank","red"],dim_cm:[14,21]},{item:"notebook",qty:50,tags:["red","blank"],dim_cm:[14,21]},{item:"paper",qty:100,tags:["red","blank","plain"],dim_cm:[14,21]},{item:"planner",qty:75,tags:["blank","red"],dim_cm:[22.85,30]},{item:"postcard",qty:45,tags:["blue"],dim_cm:[10,15.25]}]}

db.inventory.find({$expr:{$gt:[{$min:"$dim_cm"},15]}})