Database
[{"_id":ObjectId("645ccbc2a3ae372cd49cccd6"),"name":"","createdBy":"some object id","sharedWith":{"645c9bfe68c1438ef182bc26":{"write":true}}},{"_id":ObjectId("645ccbcfa3ae372cd49cccd7"),"name":"","createdBy":"some object id","sharedWith":{"645c9bfaaaaaa38ef182bc26":{"write":true}}}]
Query
db.collection.aggregate([{$set:{sharedWith_KV:{$objectToArray:"$sharedWith"}}},{$match:{"sharedWith_KV.k":"645c9bfe68c1438ef182bc26"}},{$unset:"sharedWith_KV"}])