We usually reindex everithing every hour and once a day reindex fail and put the website unusable (ALL BLANK PAGES).
We have a db that allow max 30 connections and WE CAN'T INCREASE THAT VALUE.
Thi is log error
https://i.stack.imgur.com/peXaG.jpg
We have the same website duplicated in another server with less power and the reindex work perfectly every hour.
We are currently using Magento ver. 2.3.5-p1
Thanks for the answare