I have already had the opportunity to work with MySQL, MSSQL, Oracle and, more recently, Postgres (on AWS RDS). I see no reason to choose a commercial RDBMS or

I have already had the opportunity to work with MySQL, MSSQL, Oracle and, more recently, Postgres (on AWS RDS). I see no reason to choose a commercial RDBMS or MySQL nowadays, specially when you take into account the improvements AWS Aurora or Citus are doing on top of it. Postgres is so robust and feature complete (80/20) that is my first option for relational database (and sometimes for key/value as well).