How and where is it better to store user data?

Question

MySQL

The site has a friends module. (add remove from friends)
You need to display the number of new friend requests all the time.
How and where is it better to store user data?
I think to store in memkeshe, with each new request to increase the counter. Is it right? No?
P/S development is done on yii2

Answer 1

If we are talking about high loads: Memkesh loses data on restart. Here, either store in the memcache and fill them again when the system / memcache is restarted, or store them in redis (I would do this).
In general - anywhere you can, you can at least in the same user table in MySQL - the main thing is that there is enough performance.

Answer 2

Depends on scale. You can make a table in the database with requests to friends. Delete from it applications that are accepted or rejected. In principle, subject to indexes, it should work quickly.