Database
[{"status":"in_progress","statusLog":{"received":"2010-01-01","in_progress":"2011-02-02"}}]
Query
db.collection.aggregate([{$set:{statusLog:{$objectToArray:"$statusLog"}}},{$set:{statusLog:{$filter:{input:"$statusLog",cond:{$eq:["$$this.k","$status"]}}}}},{$project:{date:{$first:"$statusLog.v"},status:1}}])