title: How does MongoDb manage CPU?
body: <p>I'm a little bit confused on how MongoDb manage it's CPU's. At the moment the general CPU is bellow 20% but I'm checking that one single CPU is always on 100%. Check MongoDb UI I can see something like this:</p>
  
  <p><a href="https://i.stack.imgur.com/DtIun.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DtIun.png" alt="enter image description here"></a></p>
  
  <p>This database has many collections (~30) and each collection has a few indexes (avg=4 per collection). I have a client that is querying one single index for a long time (and the index is always an iteration of a few records), and that's the only explanation that I can think of (although I read that mongo can execute reads in multiple threads - I'm only running read operations).  In parallel I have many other clients querying by other indexes (returning only 1 document per query), but I don't know why MongoDb is behaving like that. Does anyone have any idea on how CPU's are managed? By index? By collection? What does it mean the reading operation percentage? I can't find it anywhere.</p>
  
  <p>Thank you!</p>