“Edit/Create Post” is slow due to +40000 users

Hello,
currently, I am working on a WordPress website with more than 40k registered users.
When browsing through the admin area I found that edit/create post/page process is really slow, even that the site is hosted on a powerful VPS.
And by slow I mean 10-12 seconds until the page is completely loaded.

Screenshot1:

I check the request and it shows that the response from post.php is nearly 4MB.
The cause for this is that all of the active 40k users are displayed in a huge dropdown (options).

Screenshot2:

I tried to hide this section using the “Screen options” of the page, but it’s only hiding the HTML.

As the site admin is only one, there’s no-one else who can write/edit posts and this drop-down is simply useless. So I am looking for a way to remove it.
Any ideas/suggestions?

• This topic was modified 7 years, 1 month ago by Debugger.
• This topic was modified 7 years, 1 month ago by Debugger.