So clients would access database through samba share, is that correct? Does this work reliably with 100+ connections?

Several years ago we increased the ‘max connections’ value on our mariadb installations from the default of 100, to 5,000 .  We also moved from myisam to innodb, allowing multiple active transaction changes to the database at the same time.  We have never since had a problem with the number of database connections.  Our largest sites have about 20 PoS stations, and very busy, including with online booking too.  We also implement stress testing on databases.  So far no problems