title: How can I retrieve multiple objects by key?
body: <p>I was just looking in the <a href="https://www.firebase.com/docs/rest/guide/retrieving-data.html" rel="nofollow">docs</a> but couldn't find anything.</p>
  
  <p>So my web app has a structure that's similar to the one in this site.</p>
  
  <p>For the sake of simplicity, let's say my app has only <code>questions</code> which are catalogued by <code>tags</code>. As suggested in the docs, we store our data with a flat, non-normalized structure (E.g.</p>
  
  <pre><code>{
    "questions": {
      ...
    },
    "tags": { 
      "tag1": { 
        "name": "Tag1", 
        "questions": { "0": true, "1": true } 
      }, 
      "tag2": {
        "name": "Tag2",
        "questions": { "2": true, "3": true }
      }
    }
  }
  </code></pre>
  
  <p>), rather than a normalized structure without data replication like:</p>
  
  <pre><code>{ 
    "questions": { 
      "0": { "title": ..., "tag": ... },
      "1": { "title": ..., "tag": ... },  
     }
  }
  </code></pre>
  
  <p>One of the advantages of using the first structure is that I can search for questions that have a certain tag without downloading all the data of all of the questions first: querying for <code>/tags/tag1/questions</code>, will return all the object with all of the question's keys. Now, I can query for the questions, but how do I do that?</p>
  
  <p>I don't want to make ten requests for every question, it seems a waste of time and performance, but I couldn't find a way to make Firebase filter by multiple keys. It seems I can only give Firebase one input at a time. I think (and I hope) I am missing something here. What is it?</p>
  
  <p>If I really can't do this, how do I search by tags here? </p>