Large amount of database on disk?

Question

MySQL

I have a mysql database with 300 tables. Actively written and cleared every day via truncate (the next day's data is already irrelevant).
For a day of actual data, it runs up to 3 gigabytes, but on disk they occupy under 50 GB.
Why and what can be done about it?
There are no problems with cleaning, truncate frees up space.
All tables: a pair of ints, a pair of varchar(256) and a timestamp.

Answer 1

because the server is greedy and does not give back what it took there is an article on this topic
in the dock