Upgrade WordPress to 4.1. The admin backend the connection times out and the server gets really slow:error “The server at domain.com is taking too long to respond.”

It looks like this is actually a common issue with this version of wordpress. https://wordpress.org/support/topic/multisite-extremely-slow-after-upgrading-to-41

1) Open database via phpMyAdmin
2) Open table “wp_options” and look for “db_version” entry.
3) If that entry has a number different to “30133” (in my case it was 27916), change it to “30133”.

If you are using MU muli-sites and all the multisites are having issues, try this:

WordPress MU uses one database and each blog gets his own tables with the blog id in the prefix, so once you install a network installation your database should have these tables:

wp_1_options,wp_2_options,wp_3_options, etc. Check multisites for the same database version and change accordingly.

Check the mail options table.

mysql> SELECT option_value FROM  wp_1_options WHERE option_name = 'db_version' LIMIT 1;
+--------------+
| option_value |
+--------------+
| 30133        |
+--------------+
1 row in set (0.00 sec)

Check multisites for the same database version and change accordingly.

mysql> SELECT option_value FROM  wp_2_options WHERE option_name = 'db_version' LIMIT 1;
+--------------+
| option_value |
+--------------+
| 27916        |
+--------------+
1 row in set (0.00 sec)