Simple node+express application responses only for 64 requests

Question

Simple node+express application responses only for 64 requests

I created a simple node application for training. It should do this simple sequence of task:

check that database created, if not -- create it
put express application on port 3000
when somebody requests endpoint /:number, calculate fibonacci algorithm then put ten numbers to database and render a template with 100 first number from database

This is a source code for this app:

var express = require("express");
var jade = require('jade');

var app = express();
var db = new (require('sqlite3').verbose()).Database('data.db');

var fib = function (n) {
  if (n === 0) {
    return 0;
  } else if (n == 1) {
    return 1;
  } else {
    return fib(n - 1) + fib(n - 2)
  }
};

app.get("/:number", function (req, res) {
  var number = req.param("number"); 
  query = db.prepare("INSERT INTO data VALUES (?)");
  var result = fib(number)
  for(var i=0; i<10; i++) {
    query.run(result, function(err) {
      if(err != null) {
        throw new Error();
      }
    });
  };
  db.all("select * from data limit 100", function(err, rows){
    var rendered = jade.renderFile('template.jade', {list: rows})
    res.send(rendered); 
  });
});

db.get(
  "SELECT name FROM sqlite_master WHERE type='table' AND name='data'",
  function (err, row) {
    if(err !== null) {
      throw new Error();
    }
    if(row === undefined) {
      db.run('create table data (value text)')
    }
    app.listen(3000);
  }
);

Now I trying to test this application with wrk utility. I use the command wrk -c 64 -d 30s http://localhost:3000/10

On the first run I see this output:

Running 30s test @ http://localhost:3000/10
  2 threads and 64 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    21.37s     2.54s   22.48s    84.42%
    Req/Sec     0.91      1.82     6.00     81.82%
  64 requests in 30.01s, 78.25KB read
  Socket errors: connect 0, read 0, write 0, timeout 896

On the second output changes:

Running 30s test @ http://localhost:3000/10
  2 threads and 64 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     0.00us    0.00us   0.00us    -nan%
    Req/Sec     0.00      0.00     0.00      -nan%
  0 requests in 30.01s, 0.00B read
  Socket errors: connect 0, read 0, write 0, timeout 947

Why application doesn't response after 64's request?

node.js
express