The query_cache_size parameter was present in MySQL 5.x, but according to the manual it was removed in MySQL 8.0.3.

I have JDBC 8.0.21 installed and the MySQL database is in 8.0.13-4

(I presume you mean MySQL Connector/J 8.0.21).

I honestly don’t know where the problem is coming from.

The error will be coming from the database, but it is simply saying that the parameter is no longer recognized.

It won’t be caused by the MySQL Connector/J driver.

It is most likely caused your application (e.g. executing a SET GLOBAL query_cache_size=... or similar) or a stray option in the JDBC url that your application is using when connecting to the database.