XF 2.0 Could "Daily Clean Up" cronjob be the reason of server down?

I am having large database of thread as well as Users at my website. Right now, I am facing a issue that my server goes down for a minute and up again to specific time at 9:35. I have checked in cronjob and found that the cronjob "Daily Clean Up" start at 9:35 daily.

So just want to know -

1. How this particular cronjob works?
2. Could this be the reason of server down?

Please help and suggest.
 
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