I have a popular site
My site has a lot of visitors and the pages of the site are loaded at a very high speed
I have a section that runs every minute and receives and processes the rss content of several other sites
Just when cron is running to receive rss, the site does not respond to visitors’ requests and the pages of the site do not open, and this problem lasts for about 5 to 10 seconds until the execution of cron is finished.
The interesting thing is that the state of cpu and ram is normal when cron is running!
This happened since I updated Apache and PHP
This was not a problem in the previous version
I think I should increase the number of simultaneous connections in Apache settings
Thank you for your guidance
What should I do to fix the problem?
I emphasize again that cpu and ram status is completely normal by running cron!

I did not do anything special and I am asking for guidance here