[{"id":1,"name":"a","namespace":"a","version":"1.1.1",},{"id":2,"name":"a","namespace":"a","version":"2.1.1"},{"id":3,"name":"b","namespace":"a","version":"1.1.1"}]

db.collection.aggregate([{$sort:{"version":1}},{$group:{"_id":{"name":"$name","namespace":"$namespace"},"version":{"$last":"$version"},"object":{"$last":"$$ROOT"}}},{$sort:{"object.namespace":1,"object.name":1}},{$project:{object:1,_id:0}},{"$replaceRoot":{"newRoot":"$object"}}])