Ladsgroup added a comment.

  While I'm here, I did a quick check on matter of pressure of writes on 
master. And boy I'm not disappointed:
  
  - 6%  of all of the write pressure is just this:
  
    95904.00000000001 (6.519%) UPDATE `user` SET `user_editcount` = 
`user_editcount` + ? WHERE `user_id` = ? AND ( `user_editcount` IS NOT NULL )
  
  In other words, updating user edit count takes 6% of all of writes on master. 
This is twice as the write pressure of term store!!! I will file a bug for that.
  
  - Change dispatching costs us 5% write pressure. Maybe we can optimize it a 
bit?:
  
    76608.0 (5.208%) UPDATE `wb_changes_dispatch` SET `chd_site` = ? , `chd_db` 
= ? , `chd_seen` = ? , `chd_touched` = ? , `chd_lock` = ? WHERE `chd_site` = ?
  
  - Changes table has write pressure of 1.5 times the write pressure of the 
term store. We really should clean its design. I assume this would help a lot: 
T262856: Investigate indexes of wb_changes 
<https://phabricator.wikimedia.org/T262856>.
  
  As matter of read pressure on master, term store is 2% (nice), 11% is 
`wb_changes_subscription` (maybe needs some improvements) and the rest are core 
trying to find things to save an edit. Improving read pressure on master is 
important because it's not scalable (you can't buy more masters).
  
  I'm sorry for going a bit off-topic, this is extremely interesting.

TASK DETAIL
  https://phabricator.wikimedia.org/T246415

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To: Ladsgroup
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