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","let":{"sr_id":"$sales_reps.sales_rep_id","is_doing_well":"$sales_reps.is_doing_good"},"pipeline":[{"$match":{"$and":[{"$expr":{"$eq":["$_id","$$sr_id"]}},{"$expr":{"$eq":["$$is_doing_well",true]}}]}},{"$addFields":{"doing_good":"$$is_doing_well"}}],"as":"sales_reps"}},{"$unwind":{"path":"$sales_reps"}},{"$group":{"_id":"$_id","product":{"$first":"$$ROOT"},"sales_reps":{"$push":"$sales_reps"}},},{"$set":{"product.sales_reps":"$sales_reps"}},{"$replaceRoot":{"newRoot":"$product"}}])