db={"products":[{"_id":0,"name":"product 0","desc":"some product","sales_reps":[{"sales_rep_id":0,"is_doing_good":true},{"sales_rep_id":1,"is_doing_good":true}]}],"sales_rep_master":[{"_id":0,"name":"sales rep 0"},{"_id":1,"name":"sales rep 1"},{"_id":2,"name":"sales rep 2"}]}

db.products.aggregate([{"$match":{"_id":0}},{"$unwind":{"path":"$sales_reps"}},{"$lookup":{"from":"sales_rep_master","localField":"sales_reps.sales_rep_id","foreignField":"_id","as":"sales_rep_master"}},{"$unwind":{"path":"$sales_rep_master"}},{"$project":{"_id":1,"desc":1,"name":1,"sales_rep_master":1,"sales_reps":{"_id":"$sales_rep_master._id","name":"$sales_rep_master.name","doing_good":"$sales_reps.is_doing_good",}}},{"$group":{"_id":"$_id","desc":{"$first":"$desc"},"name":{"$first":"$name"},"sales_reps":{"$addToSet":"$sales_reps"}}}])