Express js :Handle callback in rest api

Here is what i am trying to achieve with rest API.

1.User uploads a file to AWS s3 (>20Mb).

function(req,res){
      //initiate multipart upload.with asynchronous request
      s3.multipartUpload(function(err,success){
            //when upload complete do step 2
         });
      res.send({
         'status':'pending',
         'message':'Upload is added to queue '
        });
   }

2.After the successful upload user need to add some more information about the uploaded file(Load next page to enter some meta data which will initiate another REST API).

Since the file upload is completely asynchronous how can i load the meta data screen only after the file upload??

via iam batman