Why does the VK callback API send requests to my server for a very long time?

Question

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Approximately after only 10 seconds the request comes. This problem is with any event, with messages, etc.
Node script. Tried different versions, the problem always remains. Even made the server completely clean, only a node on it.
Script:

var app = require('express')();

app.post('/адрес', function (req, res) {
  res.end("вернуть строку");
});

app.listen(80, function() {
  console.log('Port listening 80!');
});

Even updating the server address in the settings is delayed.

Answer 1

He most likely hits an error (not getting 200 ok), errors can be viewed in the public settings, api, in the requests section, the unsuccessful tab.
The problem is 99% on your side.