I would suggest tweaking the settings of this plugin to reduce such requests or contacting its developers for optimization advice.
This is the message I received this message from technical Team.
The last 3 weeks we are not able to publish contents properly because of the 503 error. This is very annoying as we are running a news website.
I am making a lot of cost as my editor can not to his work properly. He has to wait very long before he can post content (as the upload time is very slow on admin side as on website itself.
When uploading the website, homepage/page, even when posting articles we see this message.
This situation is absolutely not good for our reputation (visitors and google ranking)
So please have a look and please solve this issue as soon as possible.
We are using cloud server
Looking forward to your reply