We are seeing these errors in moderately high concurrent quizzes

[fgc]

We are receiving reports about quizzes with around 100 students having problems with wiris questions.
We have raised the max_connections parameter in configuration.ini to 50 from the original 20 (on each of our 3 load balanced front ends) but will have to monitor closely the resource consumption as the waiting processes also reserve database connections and possibly other resources.
But we think there might be some additional underlying problems with the connection queueing/pooling mechanism:
I'm attaching screenshots from a couple users. Our installation is Moodle 3.9 using PHP 7.3.11