How to remove the VK bot response delay?

Question

PHP

I made a bot based on the Callback API, I took the code here .
The problem is that sometimes there is a rather large response delay, although in other similar bots there is no such delay. Response delay - up to 3 minutes.
The functionality itself - we receive an incoming message through Callback, look for a post on the wall, send data to the user.
Server on DigitalOcean, physically in DE. I can't figure out what the problem is.
In the Callback API logs, there is this error:

Error: HTTP response code said error

Answer 1

The firewall does not let you in, the port is not configured, the repository is not configured, there is no synchronization, or it is busy and blocks as a DDOS threat, the certificate has expired (possibly an intermediate one) or force majeure. Try again later, if not, send the error log via another communication channel. Only the log is needed machine.