I will post a couple queries to help with this.
Get number of queued posts
db.objects.count({_key: "post:queue"});
Get latest 20 post queue objects ids
db.objects.find({_key: "post:queue"}).sort({score: -1}).limit(20);
Using ids from above query you can get the queued posts with
db.objects.find({_key: "post:queue:<replace_with_id_from_above_query"});
To delete a post queue from the db with id 123456
db.objects.remove({_key: "post:queue", value: "123456"});
db.objects.remove({_key: "post:queue:123456"});
To remove all queued posts
db.objects.remove({_key: /^post:queue/});
Hope that helps.