Don't know of anything wrong with MariaDB, but there used to be plenty wrong with MySQL. To give the most egregious example (THANKFULLY fixed in MariaDB, but was present in MySQL for the longest time), inserting the value 128 into a TINYINT column (signed 8-bit int) would clamp the value rather than returning an error. Which might be what you want... except if that was a primary key column. Marvel at the following, which used to be how MySQL behaved:

Note: the below taken nearly verbatim from https://sql-info.de/mysql/referential-integrity.html#3_5

  CREATE DATABASE foo;
  USE foo;
  CREATE TABLE one ( id TINYINT NOT NULL PRIMARY KEY ) TYPE=InnoDB ;
  CREATE TABLE two (
    id TINYINT NOT NULL PRIMARY KEY,
    INDEX (id),
    CONSTRAINT id_fkey FOREIGN KEY (id) REFERENCES one(id)
  ) TYPE=InnoDB ;

Now that we've created both tables, let's insert a record into table one:

  INSERT INTO one VALUES (127);

And now let's insert a record with a different primary key into table two:

  INSERT INTO two VALUES (128);

MariaDB will give you an error at this point (ERROR 1264 (22003): Out of range value for column 'id' at row 1), but MySQL (at least back when I tried this about ten years ago, which was the last time I was forced to work with MySQL — and I am so glad I never have to go back!) would return no error message and just say "Query OK, 1 row affected (0.009 sec)".

Now let's select the value we inserted into table "two":

  SELECT * FROM two;

And what do we see? The value 127, even though we inserted 128. Which has created a foreign-key relationship to table "one" that we never intended to put in there.

There are other reasons why MySQL was inadequate, but I no longer remember them. Probably MariaDB has fixed them by now. But I no longer have to use MySQL/MariaDB for anything, and I never want to go back. I have a VERY strong averse reaction, caused by past pain, when I think of using MariaDB. (I actually spun up a virtual machine to test what I wrote here, because there's no way I was going to install MariaDB on my primary work machine).

Looking Ahead to Postgres 19