Use aggregation expressions in queries with $expr - find operation

find.js

> db.accounts.find({
     $expr : { 
         $gt : [
             { $sum : ["$expenses"] },
             "$credits"
         ]
     }
 })
{ "_id" : 2, "credits" : 4000, "expenses" : [ 1000, 4000, 2000 ] }
{ "_id" : 4, "credits" : 2000, "expenses" : [ 2500, 750 ] }