[{name:"AKL to DUD Via CHC",rates:[{container_id:"abc",buyRate:380},{container_id:"def",buyRate:510}]},{name:"AKL to DUD",rates:[{container_id:"abc",buyRate:400},{container_id:"def",buyRate:420}]}]

db.collection.aggregate([{$match:{"rates.container_id":"abc"}},{$unwind:"$rates"},{$sort:{"rates.buyRate":-1}},{$group:{_id:"$_id","name":{$first:"$name"},"rates":{$push:"$rates"}}},{$sort:{"rates.buyRate":-1}}])