title: MongoDB Shard Key vs Query Index
body: <p>I have set up my first mongodb sharded cluster and am finally at the stage where I create a db/collection and choose the shard key. I’ve read about how to choose an appropriate shard key and am likely going with a hashed index but I might be having some conceptual misunderstandings.</p>
  
  <p>My documents are super simple and contain a document id (some natural number), a document version id (a natural number), and a string of the raw text itself. If I understand correctly from the documentation, I can choose to shard on the document id but this can lead to jumbo shards since the document id will be incremented and new documents will be added to the same shard. And so I could set the shard key as a hashed value of the document id.</p>
  
  <p>My question is whether or not I can still continue to query by the document id? My brain is making me doubt this and making me think that the indexing of the documents is over the hashed shard key and not over the document id. I am hoping that the hashed shard key is used strictly for sharding and that I can set any key (i.e., document id) to be indexed. Is this correct?</p>