title: Node JS Express Handling multiple requests
body: <p><strong>What I Have:</strong>
  I have a nodejs express server get endpoint that in turn calls other APIs that are time consuming(say about 2 seconds). I have called this function with a callback such that the res.send is triggered as a part of the call back. The res.send object packs an object that will be created after the results from these time consuming API calls is performed. So my res.send can only be sent when I have the entire information from the API call.</p>
  
  <p>Some representative code.</p>
  
  <pre><code>someFunctionCall(params, callback)
  {
    // do some asyncronous requests.
    Promise.all([requestAsync1(params),requestAsync2(params)]).then
    {
       // do some operations
       callback(response) // callback given with some data from the promise
    }
  
  }
  app.get('/',function(req, res){
   someFunctionCall(params, function(err, data){
      res.send(JSON.stringify(data))
     }
  }
  </code></pre>
  
  <p><strong>What I want</strong>
  I want my server to be able to handle other parallel incoming get requests without being blocked due to the REST api calls in the other function. But the problem is that the callback will only be issued when the promises are fulfilled,each of those operations are async, but my thread will wait till the execution of all of them. And Node does not accept the next get request without executing the res.send or the res.end of the previous request. This becomes an issues when I have multiple requests coming in, each one is executed one after another.</p>
  
  <p>Note: I do not want to go with the cluster method, I just want to know if it is possible to this without it. </p>