test.js

db.website_performance.aggregate(
[
  { $match : { 'domain' : { $in: ['xxx.com','porntube.com']} } },
  { $group: {
      _id: '$domain',
      sum_impressions: { $sum: "$impressions" },
      sum_bids: { $sum: "$bids" },
      sum_clicks: {$sum: "$clicks"},
      sum_leads: {$sum: "$leads"},
      sum_actual_cost: {$sum: "$actual_cost"},
      sum_total_offered: {$sum: "$total_offered"},
      sum_revenue: {$sum: "$revenue"}
    }
  },
  { $project: {
      sum_bids : 1,
      sum_impressions : 1,
      sum_clicks : 1,
      sum_leads : 1,
      total_offered : { $divide : [ '$sum_total_offered', 1000000000 ] },
      total_cost : { $divide : [ '$sum_actual_cost' , 1000000 ] },
      total_revenue : { $divide : [ '$sum_revenue', 1000000 ] }
      
    }
  },
  { $sort: { sum_leads: -1 } }
]);

db.website_performance.ensureIndex({domain: 1})