Has anyone else suffered from this?
I used to have a WP basic install. CPU usage was normal.
Updated to Redis and after a few hours the Nginx CPU usage goes to 100%. Restart Nginx and it is normal, but then usage goes back up to 100% over the next few hours.
So now I updated the site to Fast CGI and CPU usage is back to normal.
The site is relatively high traffic, around 80K visitors every day. I also run WP-Rocket with page caching off (i.e. just for CSS and JS minification and lazy loading).