Why are there long delays in the response of the bot in Telegram?

Question

PHP

Wrote a bot for telegram. I am using webhook. Very long delays in response to a request from the bot. Sometimes he answers quickly. What could be the problem? The server is not under network load. All other server services work normally without delay. It is when using calls to the bot through telegrams that long delays occur.
PS There is a suspicion that the problem is in the self-signed certificate. put a certificate from Let's Encrypt - everything began to work smartly.

Answer 1

Changing the SSL certificate from self-signed to Let's Encrypt helped. The delays have stopped.

Answer 2

I'm afraid that this is a telegram problem and not yours, when I was analyzing messages, the delays from the moment the message was sent to the user receiving them were up to a minute (although in my case we are talking about a regular client slightly modified to work with events, and not official bots , who can only be admins/owners of the chat).