c.find({a: {$gt: 10}}, {sort: {b: -1, a: 1}, limit: 5}).fetch(), [
      {a: 11, b: 1, _id: '11_1'},
      {a: 12, b: 1, _id: '12_1'},
      {a: 13, b: 1, _id: '13_1'},
      {a: 14, b: 1, _id: '14_1'},