We run a high traffic blog with around 500 real-time users and 10000 posts. We are hosted by self on VPS - 16gb, 4 core with separate mysql DB server - 4gb, 2 core; both SSD. No problem with hosting server But the database server at times running out of connections, though we have more than sufficient 312 max cconnections ceiling. We don't have any stray plugins and our maximum execution time is around 5 minutes. Anyone have any idea regarding what might be causing the issue.
More insights: What we could correlate is that the days when our bloggers (max 10) work from our office under a single IP and slow -interrupted network connection this issue happens to be more frequent. The issue is more frequent at peak publishing hours than during idle hours.
Or is the database server running out of ram which is eventually causing the connections blackout. Search engine crawls usually drink more Cpu but the bots don't establish more than 30 db connections and our servers are totally fine handling the bots.
Also prevelant when a single admin keep the posts in edit mode for long periods of time
wp config details
'WP_MEMORY_LIMIT', '256M; 'AUTOSAVE_INTERVAL', 160; max_execution time 500
Our query monitor has some PHP 7.2 depreciation warnings though the theme is stable with some slow queries, also posts revisions are vital for us.