title: MongoDB: what is faster: single find() query or many find_one()?
body: <p>I have the following problem connected to the MongoDB database design. Here is my situation:</p>
  
  <ul>
  <li>I have a collection with about 50k documents (15kB each),</li>
  <li>every document have a dictionary storing data samples,</li>
  <li>my query always gets all the data from the document,</li>
  <li>every query uses an index,</li>
  <li>the collection have only one index (based on a single datetime field),</li>
  <li>in most cases, I need to get data from many documents (typically 25 &lt; N &lt; 100),</li>
  <li>it is easier for me to perform many SELECT queries over a single one,</li>
  <li>I have a lot of updates in my databases, much less than SELECT ones,</li>
  <li>I use the WiredTiger engine (the newest version of MongoDB),</li>
  <li>server instance and web application are on the same machine.</li>
  </ul>
  
  <p>I have two possibilities for making a SELECT query:</p>
  
  <ul>
  <li>perform a single query retrieving all documents I am interested in,</li>
  <li>perform N queries, everyone gets a single document, where typically 25 &lt; N &lt; 100 (what about a different scenario when 100 &lt; N &lt; 1k or 1k &lt; N &lt; 10k?)</li>
  </ul>
  
  <p><strong>So the question is if there is any additional overhead when I perform many small queries over a single one?</strong> In relational databases making many queries is a very bad practice - but in NoSQL? I am asking about a general practice - should I avoid that much queries?</p>
  
  <p>In the documentation, I read that the number of queries is not important but the number of searches over documents - is that true?</p>
  
  <p>Thanks for help ;)</p>