What is the best way to implement event counters on the site?

Question

Software design

Good afternoon!
I have a portal, it has users. Users generate a certain number of events, entities.
There are several places where I need to display the number of new entities for the user, conditionally - counters.
The simplest example of what I need is to highlight chat channels in which there are new messages for the user and, ideally, write how many of them are there.
How would you implement it yourself?
From tools - django + mysql + memcached