make wordpress work better for big site

Hi All

it looks like wordpress could not really handle a website that has a lot of post?

We have imported 660K posts forum into bbpress, as you know, bbpress’s topic is “post” on DB. WordPress ‘s /wp-admin works so BAD for any mass move/delete/trash functions

e.g. , I now want to remove a forum with 56 topics ONLY, I click “trash” on WP’s /wp-admin, it simply HANGS. It is crazily slow and it never ends done… I could not imagine one day when we need to delete forum spammer’s posts, how slow it will be

I am ware of that there are some mass move/delete plugins, but they are NOT helpful because sometimes we want to pick scattered topics from everywhere , let’s say 10 topics, WP just hangs and It looks like system go over 600K posts in order to pick up those 10

We submit a request on
https://bbpress.org/forums/topic/make-bbpress-work-better-for-big-forum/

ppl says it is WP ‘s core issue related to oSELECT SQL_CALC_FOUND_ROWS

please make wordpress work better for big site or if you have any tips, please do tell

our server
Dedicated server
12 cores
Intel SSD
48G ram
PHP 5.5
MySQL 5.6

I do not think any tweaking will help on this issue even we have also done a lot

thanks