Database
db={user:[{_id:ObjectId("5fedda064c9073b6289e8eaf")},{_id:ObjectId("6398c34ca67dbe3286452f23")}],interaction:[{blocked:{5fedda064c9073b6289e8eaf:true,5fedda064c9073b6289e8ea6:true}},{blocked:{5fedda064c9073b6289e8ea2:true,5fedda064c9073b6289e8ea6:true}}]}
Query
db.user.aggregate([{$lookup:{from:"interaction",as:"remove",let:{tar_id:{$toString:"$_id"}},pipeline:[{$match:{$expr:{$gt:[{$size:{$filter:{input:{$objectToArray:"$blocked"},cond:{$eq:["$$tar_id","$$this.k"]}}}},0]}}},{$limit:1},{$project:{_id:0,remove:"true"}}]}}])